Parallax Corrected Cubemaps

What Is This?

By default, Source's cubemaps are naively reflected on the ground and do not follow the player's perspective. This causes an unrealistic-looking reflection for most surfaces. A possible solution can be to parallax-correct the cubemaps based on the player's camera position, using a custom shader and a bounding box trigger for a cubemap. This tutorial, based directly on the work of Brian Charles, will show you how to do just that.

Brian Charles' video that showcases the before and after of this tutorial can be found here: Parallax Corrected Cubemaps in the Source Engine

The Code

Before starting, we'll need this file:

• matrixinvert.h

Which you'll put into <src code directory>/src/utils/vbsp/

Now let's jump right into it, shall we?

Go into your everything.sln solution and open cubemap.cpp

cubemap.cpp

Now add this under (not inside) the SideHasCubemapAndWasntManuallyReferenced( int iSide ) function:

char *g_pParallaxObbStrs[MAX_MAP_CUBEMAPSAMPLES];

Then right below, change the CubeMap_InsertSample( ... ) function to look like this:

void Cubemap_InsertSample( const Vector &origin, int size, char *pParallaxObbStr = "" )

And inside that function, at the very top add this:

g_pParallaxObbStrs[g_nCubemapSamples] = pParallaxObbStr;

Now go down to the PatchEnvmapForMaterialAndDependents( ... ) function and change it to look like this:

static bool PatchEnvmapForMaterialAndDependents( const char *pMaterialName, const PatchInfo_t &info, const char *pCubemapTexture, const char *pParallaxObbMatrix = "" )

While in the same function, scroll a tiny bit down to the if ( pDependentMaterial ) statement and change the line in it to this:

	bDependentMaterialPatched = PatchEnvmapForMaterialAndDependents( pDependentMaterial, info, pCubemapTexture, pParallaxObbMatrix );

Scroll a tiny bit down again until you find this line:

	MaterialPatchInfo_t pPatchInfo[2];

Then just change 2 to 6, like so:

	MaterialPatchInfo_t pPatchInfo[6];

Do another tiny scroll down, and above this line:

	char pDependentPatchedMaterialName[1024];

Add:

	// Parallax cubemap matrix
	CUtlVector<char *> matRowList;
	if ( pParallaxObbMatrix[0] != '\0' )
	{
		V_SplitString( pParallaxObbMatrix, ";", matRowList );
	
		pPatchInfo[nPatchCount].m_pKey = "$envMapParallaxOBB1";
		pPatchInfo[nPatchCount].m_pValue = matRowList[0];
		++nPatchCount;
		pPatchInfo[nPatchCount].m_pKey = "$envMapParallaxOBB2";
		pPatchInfo[nPatchCount].m_pValue = matRowList[1];
		++nPatchCount;
		pPatchInfo[nPatchCount].m_pKey = "$envMapParallaxOBB3";
		pPatchInfo[nPatchCount].m_pValue = matRowList[2];
		++nPatchCount;
		pPatchInfo[nPatchCount].m_pKey = "$envMapOrigin";
		pPatchInfo[nPatchCount].m_pValue = matRowList[3];
		++nPatchCount;
	}

At the bottom of the function you'll find this line:

	CreateMaterialPatch( pMaterialName, pPatchedMaterialName, nPatchCount, pPatchInfo, PATCH_REPLACE );

Change it to this:

	CreateMaterialPatch( pMaterialName, pPatchedMaterialName, nPatchCount, pPatchInfo, PATCH_INSERT );

Then below that add this:

	// Clean up parallax stuff
	matRowList.PurgeAndDeleteElements();

Scroll down to the Cubemap_CreateTexInfo( ... ) function and change it to this:

static int Cubemap_CreateTexInfo( int originalTexInfo, int origin[3], int cubemapIndex )

Scroll a bit down inside that function and find this line:

	GeneratePatchedName( "c", info, false, pTextureName, 1024 );

Now below that line add this:

	// Append origin info if this cubemap has a parallax OBB
	char originAppendedString[1024] = "";
	if ( g_pParallaxObbStrs[cubemapIndex][0] != '\0' )
	{
		Q_snprintf( originAppendedString, 1024, "%s;[%d %d %d]", g_pParallaxObbStrs[cubemapIndex], origin[0], origin[1], origin[2] );
	}

A bit down you'll see this if statement:

	if ( !PatchEnvmapForMaterialAndDependents( pMaterialName, info, pTextureName ) )

Change it to:

	if ( !PatchEnvmapForMaterialAndDependents( pMaterialName, info, pTextureName, originAppendedString ) )

Scroll down until you find the Cubemap_FixupBrushSidesMaterials( void ) function, and inside it find this line:

	pSide->texinfo = Cubemap_CreateTexInfo( pSide->texinfo, g_CubemapSamples[cubemapID].origin );

Change it to this:

	pSide->texinfo = Cubemap_CreateTexInfo( pSide->texinfo, g_CubemapSamples[cubemapID].origin, cubemapID );

Scroll down to the Cubemap_AttachDefaultCubemapToSpecularSides( void ) function, and inside it find this line:

	pSide->texinfo = Cubemap_CreateTexInfo( pSide->texinfo, g_CubemapSamples[iCubemap].origin );

Change it to this:

	pSide->texinfo = Cubemap_CreateTexInfo( pSide->texinfo, g_CubemapSamples[iCubemap].origin, iCubemap );

Now we're done with cubemap.cpp, we can now move over to vbsp.h

vbsp.h

Now find this line:

void Cubemap_InsertSample( const Vector& origin, int size );

And change it to this:

void Cubemap_InsertSample( const Vector &origin, int size, char *pParallaxObbStr );

And above that add this:

extern char *g_pParallaxObbStrs[MAX_MAP_CUBEMAPSAMPLES];

Now we're done with vbsp.h, now let's go into map.cpp

map.cpp

At the very top, add this include:

#include "matrixinvert.h"

Then scroll down to the LoadEntityCallback( ... ) function, then inside it find this line:

	const char *pSideListStr = ValueForKey( mapent, "sides" );

Now below that line, add:

	char *pParallaxObbStr = ValueForKey( mapent, "parallaxobb" );

Then a tiny bit down find this line:

	Cubemap_InsertSample( mapent->origin, size );

And change it to this:

	Cubemap_InsertSample( mapent->origin, size, pParallaxObbStr );

Now below the parent if statement we're in, add this:

	//
	// parallax_obb brushes are removed after the transformation matrix is found and saved into 
	// the entity's data (ent will be removed after data transferred to patched materials)
	//
	if ( !strcmp( "parallax_obb", pClassName ) )
	{
		matrix3x4_t obbMatrix, invObbMatrix;
		SetIdentityMatrix( obbMatrix );
		SetIdentityMatrix( invObbMatrix );

		// Get corner and its 3 edges (scaled, local x, y, and z axes)
		mapbrush_t *brush = &mapbrushes[mapent->firstbrush];
		Vector corner, x, y, z;

		// Find first valid winding (with these whiles, if not enough valid windings then identity matrix is passed through to VMTs)
		int i = 0;
		while ( i < brush->numsides )
		{
			winding_t *wind = brush->original_sides[i].winding;
			if ( !wind )
			{
				i++;
				continue;
			}

			corner = wind->p[0];
			y = wind->p[1] - corner;
			z = wind->p[3] - corner;
			x = CrossProduct( y, z ).Normalized();

			i++;
			break;
		}

		// Skip second valid winding (opposite face from first, unusable for finding Z's length)
		while ( i < brush->numsides )
		{
			winding_t *wind = brush->original_sides[i].winding;
			if ( !wind )
			{
				i++;
				continue;
			}
			i++;
			break;
		}

		// Find third valid winding
		while ( i < brush->numsides )
		{
			winding_t *wind = brush->original_sides[i].winding;
			if ( !wind )
			{
				i++;
				continue;
			}

			// Find length of X
			// Start with diagonal, then scale X by the projection of diag onto X
			Vector diag = wind->p[0] - wind->p[2];
			x *= abs( DotProduct( diag, x ) );

			// Build transformation matrix (what is needed to turn a [0,0,0] - [1,1,1] cube into this brush)
			MatrixSetColumn( x, 0, obbMatrix );
			MatrixSetColumn( y, 1, obbMatrix );
			MatrixSetColumn( z, 2, obbMatrix );
			MatrixSetColumn( corner, 3, obbMatrix );

			// Find inverse (we need the world to local matrix, "transformationmatrix" is kind of a misnomer)
			MatrixInversion( obbMatrix, invObbMatrix );
			break;
		}
			
		char szMatrix[1024];
		Q_snprintf( szMatrix, 1024, "[%f %f %f %f];[%f %f %f %f];[%f %f %f %f]", invObbMatrix[0][0], invObbMatrix[0][1], invObbMatrix[0][2], invObbMatrix[0][3], invObbMatrix[1][0], invObbMatrix[1][1], invObbMatrix[1][2], invObbMatrix[1][3], invObbMatrix[2][0], invObbMatrix[2][1], invObbMatrix[2][2], invObbMatrix[2][3] );
		SetKeyValue( mapent, "transformationmatrix", szMatrix );

		return ( ChunkFile_Ok );
	}

Now scroll down to the LoadMapFile( ... ) function, inside it scroll down until you find this line:

	if ((eResult == ChunkFile_Ok) || (eResult == ChunkFile_EOF))

Now above that line, add this:

	// Fill out parallax obb matrix array
	for ( int i = 0; i < g_nCubemapSamples; i++ )
	{
		if ( g_pParallaxObbStrs[i][0] != '\0' )
		{
			entity_t *obbEnt = EntityByName( g_pParallaxObbStrs[i] );
			g_pParallaxObbStrs[i] = ValueForKey( obbEnt, "transformationmatrix" );
		}
	}

	// Remove parallax_obb entities (in a nice slow linear search)
	for ( int i = 0; i < g_MainMap->num_entities; i++ )
	{
		entity_t *mapent = &g_MainMap->entities[i];
		const char *pClassName = ValueForKey( mapent, "classname" );
		if ( !strcmp( "parallax_obb", pClassName ) )
		{
			mapent->numbrushes = 0;
			mapent->epairs = NULL;
		}
	}

And that should be it! Try compiling the VBSP project, it should compile without any errors.

Now all that's left is moving the freshly compiled vbsp.exe file to your game's bin/ folder.

The Shaders

Now, the fun stuff: shader editing! The Parallax Corrected Cubemaps that will now be patched into your materials need a custom LightmappedGeneric shader for them to be properly displayed.

Let's start simple. To edit shaders, you'll need to open your everything.sln file. Bonus points if you already had it open!

Warning:This section is the lengthiest and most tedious, just due to having to compile a custom LightmappedGeneric shader, which can take upwards of 30 minutes per compile, even on beefy computers!

Note:It's recommended to follow the Shader Authoring tutorial to get set up with the wonderful DirectX 2008 SDK, and a feel for compiling shaders. This tutorial assumes you're comfortable with that.

Warning:Valve does not like when you override default shaders in the SDK 2013 project. Therefore, we will be creating identical shaders to the LightmappedGeneric one, just with the SDK_ prefix.

Shader C++ Files

Firstly, let's get the LightmappedGeneric shader familiar with the Parallax Corrected bounding boxes you stored in the material.

lightmappedgeneric_dx9_helper.h

Add the following lines to the end of the LightmappedGeneric_DX9_Vars_t struct (after the int m_nOutlineEnd1; member):

	// Parallax cubemaps
	int m_nEnvmapParallaxObb1;
	int m_nEnvmapParallaxObb2;
	int m_nEnvmapParallaxObb3;
	int m_nEnvmapOrigin;

lightmappedgeneric_dx9.cpp

As warned about before, we need to turn this into an SDK shader, since compiling a default LightmappedGeneric shader works, but you can't use it in-game. Change the line:

BEGIN_VS_SHADER( LightmappedGeneric,
				 "Help for LightmappedGeneric" )

to be:

BEGIN_VS_SHADER( SDK_LightmappedGeneric, "Help for SDK_LightmappedGeneric" )

Now we need the implementation file to populate these shader parameters. Add the following lines inside of the

BEGIN_SHADER_PARAMS

block at the top of this file, after the

	SHADER_PARAM( OUTLINEEND1, SHADER_PARAM_TYPE_FLOAT, "0.0", "outer end value for outline")

line:

	// Parallax cubemaps
	SHADER_PARAM( ENVMAPPARALLAXOBB1, SHADER_PARAM_TYPE_VEC4, "[1 0 0 0]", "The first line of the parallax correction OBB matrix" )
	SHADER_PARAM( ENVMAPPARALLAXOBB2, SHADER_PARAM_TYPE_VEC4, "[0 1 0 0]", "The second line of the parallax correction OBB matrix" )
	SHADER_PARAM( ENVMAPPARALLAXOBB3, SHADER_PARAM_TYPE_VEC4, "[0 0 1 0]", "The third line of the parallax correction OBB matrix" )
	SHADER_PARAM( ENVMAPORIGIN, SHADER_PARAM_TYPE_VEC3, "[0 0 0]", "The world space position of the env_cubemap being corrected" )

If you did your homework in the Shader Authoring section, you'll know that this is defining the shader parameters inside of the material file. Now let's assign them to the struct's new members. In the same file, inside of the

void SetupVars( LightmappedGeneric_DX9_Vars_t& info )

function, add the following lines at the end of it (after the info.m_nOutlineEnd1 = OUTLINEEND1; line):

	// Parallax cubemaps
	info.m_nEnvmapParallaxObb1 = ENVMAPPARALLAXOBB1;
	info.m_nEnvmapParallaxObb2 = ENVMAPPARALLAXOBB2;
	info.m_nEnvmapParallaxObb3 = ENVMAPPARALLAXOBB3;
	info.m_nEnvmapOrigin = ENVMAPORIGIN;

Great, now our shader's code knows about our patched parameters. But we still have to do stuff with them!

lightmappedgeneric_dx9_helper.cpp

As mentioned before, again, we need to change some prefixes. For your includes, change the lines:

#include "lightmappedgeneric_ps20.inc"
#include "lightmappedgeneric_vs20.inc"
#include "lightmappedgeneric_ps20b.inc"

to be:

#include "SDK_lightmappedgeneric_ps20.inc"
#include "SDK_lightmappedgeneric_vs20.inc"
#include "SDK_lightmappedgeneric_ps20b.inc"

You'll generate these in a bit, don't worry. But now this will cause some more issues further in the code! You'll need to replace all instances of the code of the default shader with your newly copied SDK one.

For example:

	DECLARE_STATIC_VERTEX_SHADER( lightmappedgeneric_vs20 );

to:

	DECLARE_STATIC_VERTEX_SHADER( sdk_lightmappedgeneric_vs20 );

DO IT FOR EVERY INSTANCE! Changing the imports will help when you come back to compile this module in a bit, as the old lightmappedgeneric_* shaders will be underlined red, as to help you find where you missed a specific spot.

Firstly, let's do a safety check. We need to ensure we have all the required components for the Parallax Corrected Cubemaps to work properly. Inside of

void InitParamsLightmappedGeneric_DX9( CBaseVSShader *pShader, IMaterialVar** params, const char *pMaterialName, LightmappedGeneric_DX9_Vars_t &info )

near the top of this file, add the following lines of code to the (you guessed it) end of it, after the InitFloatParam( info.m_nOutlineAlpha, params, 1.0 ); line:

	// Parallax cubemaps
	// Cubemap parallax correction requires all 4 lines (if the 2nd, 3rd, or 4th are undef, undef the first one (checking done on first var)
	if ( !( params[info.m_nEnvmapParallaxObb2]->IsDefined() && params[info.m_nEnvmapParallaxObb3]->IsDefined() && params[info.m_nEnvmapOrigin]->IsDefined() ) )
	{
		params[info.m_nEnvmapParallaxObb1]->SetUndefined();
	}

This allows the parallax-correcting code to not run if there's some issue with your patched materials or something.

Next, we need to tell the shader itself whether the above code we added returns true, and if so, to render the parallax corrected cubemap. Inside the

void DrawLightmappedGeneric_DX9_Internal( ... )

function, after the line

	bool hasNormalMapAlphaEnvmapMask = IS_FLAG_SET( MATERIAL_VAR_NORMALMAPALPHAENVMAPMASK );

add the following boolean declaration:

	// Parallax cubemaps
	bool hasParallaxCorrection = params[info.m_nEnvmapParallaxObb1]->IsDefined();

Now let's check this boolean. Further down this gargantuan function, we need to set the combo on the pixel shader. Inside of the

	if ( g_pHardwareConfig->SupportsPixelShaders_2_b() )

block, add the following line BEFORE the

	SET_STATIC_PIXEL_SHADER( sdk_lightmappedgeneric_ps20b );

line:

	// Parallax cubemaps enabled for 2_0b and onwards
	SET_STATIC_PIXEL_SHADER_COMBO( PARALLAXCORRECT, hasParallaxCorrection );

If you're able to read, you can start to realize what we're going to do next: since Shader Model 2.0 was all the rage for the GoldSource days, and something like parallax corrected cubemaps is a little high-tech for it, we need to enable it only if the graphics card running the engine supports Shader Model 2.0b (and higher). So a little further in this mega-function, inside of the else statement for the code above, RIGHT BEFORE the line SET_STATIC_PIXEL_SHADER( sdk_lightmappedgeneric_ps20 );, add the following:

	// Parallax cubemaps
	SET_STATIC_PIXEL_SHADER_COMBO( PARALLAXCORRECT, 0 ); // No parallax cubemaps with ps_2_0 :(

So now our pixel shader (which we're editing next section) knows whether or not it should handle the parallax corrected cubemaps.

Lastly, but certainly not least-ly (I mean come on we still haven't even edited the shader yet!), we need to send the pixel shader the proper value to use to display our parallax-corrected cubemap. So, even further down in this hulking hunk of hot garbage function, RIGHT BEFORE the pContextData->m_SemiStaticCmdsOut.End(); line, add the following block of code:

	// Parallax cubemaps
	if ( hasParallaxCorrection )
	{
		pContextData->m_SemiStaticCmdsOut.SetPixelShaderConstant( 21, params[info.m_nEnvmapOrigin]->GetVecValue() );

		float *vecs[3];
		vecs[0] = const_cast<float *>( params[info.m_nEnvmapParallaxObb1]->GetVecValue() );
		vecs[1] = const_cast<float *>( params[info.m_nEnvmapParallaxObb2]->GetVecValue() );
		vecs[2] = const_cast<float *>( params[info.m_nEnvmapParallaxObb3]->GetVecValue() );
		float matrix[4][4];
		for ( int i = 0; i < 3; i++ )
		{
			for ( int j = 0; j < 4; j++ )
			{
				matrix[i][j] = vecs[i][j];
			}
		}
		matrix[3][0] = matrix[3][1] = matrix[3][2] = 0;
		matrix[3][3] = 1;
		pContextData->m_SemiStaticCmdsOut.SetPixelShaderConstant( 22, &matrix[0][0], 4 );
	}

Woo! Now our shader has the right data passed into it. Alright, time to put on your DirectX 8 hats, we're going in!

The Shader Files

lightmappedgeneric_ps2_3_x.h

Now, I know what you're thinking. This isn't anywhere close to a shader file! It's a gosh dang C++ header file! But worry not, this file is included inside of the next file we edit, the actual shader source (FXC) file. So all of this code will actually get compiled into the shader, making it a shader source in disguise!

First things first, let's declare us some registers to snag up. If you're wondering why this shader doesn't work with Shader Model 2.0, here is why. Inside this file, right below

const float4 g_ShadowTweaks : register( c19 );

add:

// Parallax cubemaps
#if ( PARALLAXCORRECT )
const float3 g_CubemapPos : register( c21 );
const float4x4 g_ObbMatrix : register( c22 ); // Through c25
#endif

Don't worry about that PARALLAXCORRECT, it'll make sense in a bit.

Now, let's do the main shader math we need! We can skip further down the file, and find where cubemaps are processed, inside of the if( bCubemap ) block, add the following block of code after the fresnel = fresnel * g_OneMinusFresnelReflection + g_FresnelReflection; line:

	// Parallax correction (2_0b and beyond)
	// Adapted from http://seblagarde.wordpress.com/2012/09/29/image-based-lighting-approaches-and-parallax-corrected-cubemap/
#if !( defined( SHADER_MODEL_PS_1_1 ) || defined( SHADER_MODEL_PS_1_4 ) || defined( SHADER_MODEL_PS_2_0 ) )
#if ( PARALLAXCORRECT )
	float3 worldPos = i.worldPos_projPosZ.xyz;
	float3 positionLS = mul( float4( worldPos, 1 ), g_ObbMatrix );
	float3 rayLS = mul( reflectVect, (float3x3)g_ObbMatrix );

	float3 firstPlaneIntersect = ( float3( 1.0f, 1.0f, 1.0f ) - positionLS ) / rayLS;
	float3 secondPlaneIntersect = ( -positionLS ) / rayLS;
	float3 furthestPlane = max( firstPlaneIntersect, secondPlaneIntersect );
	float distance = min( furthestPlane.x, min( furthestPlane.y, furthestPlane.z ) );

	// Use distance in WS directly to recover intersection
	float3 intersectPositionWS = worldPos + reflectVect * distance;
	reflectVect = intersectPositionWS - g_CubemapPos;
#endif
#endif

Wonderful. Our shader will now properly do fancy maths to parallax the cubemap based on the player's position. Onwards to the FXC file!

A Shader By Any Other Name

You'll then need to make a copy of these files:

lightmappedgeneric_ps2x.fxc
lightmappedgeneric_ps11.fxc
lightmappedgeneric_vs20.fxc

And then rename the copies to:

SDK_lightmappedgeneric_ps2x.fxc
SDK_lightmappedgeneric_ps11.fxc
SDK_lightmappedgeneric_vs20.fxc

SDK_lightmappedgeneric_ps2x.fxc

Heck yeah, here we go, shader file editing! Told you we'd get here! Alright, you ready? Brace yourself, these edits are such a doozy.

Add the following line, after // STATIC: "FLASHLIGHT" "0..1" [ps20b] [XBOX]:

// STATIC: "PARALLAXCORRECT" "0..1"

This is declaring the static combo that our code from the previous section declares. But hold on tight, we still got more!

We need to optimize the shader to not compile under certain conditions. For example, when shadercompile is working on the Shader Model 2.0 version, we can tell it not to build the version with the Parallax Corrected Cubemaps inside of it. Similarly, if there isn't even a dang cubemap to begin with, we don't want the parallax-correcting code to run! So after the line // SKIP ($DETAIL_BLEND_MODE == 11 ) && ($BUMPMAP != 0 ), add:

// SKIP: $PARALLAXCORRECT && !$CUBEMAP
// SKIP: $PARALLAXCORRECT [ps20]

That's all there is to it! You can open your eyes now. Actually, hopefully, they were open for all of this tutorial, because otherwise, you will be getting very interesting results.

Compile the Shader(s)

Note:Psst, if you need extra help with this section, look at the Your First Shader page, it's a pretty good resource for compiling shaders!

Now we need to compile the shader. Got some coffee to go make? Some meal to go prepare? Some arbitrary 30-minute task? Good! Compiling a custom LightmappedGeneric shader is going to take roughly that time. Any time you need to change anything with the shader, it'll take 30 minutes to fully recompile it! So, hopefully, this works on the first try.

Inside of your stdshader_dx9_20b.txt file (or your custom game one, I don't judge), make sure that the following shaders are added:

SDK_lightmappedgeneric_ps2x.fxc
SDK_lightmappedgeneric_ps11.fxc
SDK_lightmappedgeneric_vs20.fxc

Now, compile. Go do that task I was asking you about. It's gonna take a while because it's a Perl script compiling one of the more complex shaders, so it has a lot of combinations to go through. It's going to use all of your resources, too, so don't get spooked. Is it winter? Good, it'll warm up your room.

When it completes, it will generate the proper SDK_lightmappedgeneric_*.inc files that your code uses, and you should have your SDK_lightmappedgeneric_*.vcs files inside of the shaders/fxc/ subdirectory. You can copy these over to your game's shaders/fxc/ folder.

With your new .inc files, you should be able to compile the game_shader_dx9 project. Ensure the naming of everything matches! If you are missing an SDK_* include, try looking for the file and make sure it's named properly! With the project compiled, you will have a nifty game_shader_dx9.dll to copy over to your game's bin/ folder, alongside your server and client DLLs.

What Next?

Using the new SDK_LightmappedGeneric Shader

Now, since Valve doesn't allow the SDK 2013 branch to override the default LightmappedGeneric shader, you're going to either need to stub the materialsystem and manually replace all of the shaders, or just create/copy VMTs that use the shader.

The FGD File

parallaxcubes.fgd:

@include "YOUR FGD HERE. THIS ONE WILL OVERRIDE THE REGULAR ENV_CUBEMAP ENTITY AND ALSO ADD THE PARALLAX_OBB ENTITY. ONLY INCLUDE THIS ONE IN HAMMER."

@PointClass color(0 0 255) sidelist(sides) iconsprite("editor/env_cubemap.vmt") = env_cubemap : 
	"An entity that creates a sample point for the Cubic Environment Map."
[
	cubemapsize(choices) : "Cubemap Size" : 0 =
	[
		0 : "Default"
		1 : "1x1"
		2 : "2x2"
		3 : "4x4"
		4 : "8x8"
		5 : "16x16"
		6 : "32x32"
		7 : "64x64"
		8 : "128x128"
		9 : "256x256"
	]
	sides(sidelist) : "Brush faces": : "(Optional) Brushes faces to directly attach to the env_cubemap. Press Pick then click on faces in the 3D View to select them. Use CTRL while clicking to add or remove from the selection."
	parallaxobb(target_destination) : "Cubemap Bounds" : : "(Optional) assigns this cubemap a bounding box for parallax correction (brush entity tied to parallax_obb)."
]

@SolidClass = parallax_obb
[
	targetname(target_source) : "Name" : : "The name that other entities refer to this entity by."
]

(Optional) Test Map

Todo: Coming soon

Conclusion

And that's it, try launching your mod to see if it works!

This is currently only tested on the SP branch of Source SDK 2013. The MP branch and Source SDK 2007 remain untested as of writing this article.