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Optimize shader code #1323

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782bec6
Optimize shaders: loop-based matrix unpacking and branchless lookup t…
adfriz May 27, 2026
07e74a4
Optimize shaders: skip unpacking for static vertices and use hardware…
adfriz May 27, 2026
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112 changes: 20 additions & 92 deletions assets/Shaders/default.vert
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Original file line number Diff line number Diff line change
Expand Up @@ -99,107 +99,35 @@ vec4 getLightResult()

vec3 transformVector(vec3 initialVector, int matrixIndex)
{
float X = (initialVector.x * modelMatricies[matrixIndex][0].x) + (initialVector.y * modelMatricies[matrixIndex][1].x) + (initialVector.z * modelMatricies[matrixIndex][2].x);
float Y = (initialVector.x * modelMatricies[matrixIndex][0].y) + (initialVector.y * modelMatricies[matrixIndex][1].y) + (initialVector.z * modelMatricies[matrixIndex][2].y);
float Z = (initialVector.x * modelMatricies[matrixIndex][0].z) + (initialVector.y * modelMatricies[matrixIndex][1].z) + (initialVector.z * modelMatricies[matrixIndex][2].z);
// ignoreW per DirectX

X += 1 * modelMatricies[matrixIndex][3].x;
Y += 1 * modelMatricies[matrixIndex][3].y;
Z += 1 * modelMatricies[matrixIndex][3].z;
return vec3(X, Y, Z);
// ignoreW per DirectX by casting vec4 result to vec3
return vec3(modelMatricies[matrixIndex] * vec4(initialVector, 1.0));
}

void main()
{
vec3 pos = vec3(iPosition);
oColor = iColor;

if(iMatrixChain.x != 0)
{
// unpack packed matrix indicies
int m0 = (iMatrixChain.x & (0xff << 24)) >> 24;
int m1 = (iMatrixChain.x >> 16) & 0xff;
int m2 = (iMatrixChain.x & 0xff00) >> 8;
int m3 = (iMatrixChain.x & 0xff);

if(m0 >=0 && m0 < 255)
{
pos = transformVector(pos, m0);
}

if(m1 >=0 && m1 < 255)
{
pos = transformVector(pos, m1);
}

if(m2 >=0 && m2 < 255)
{
pos = transformVector(pos, m2);
}

if(m3 >=0 && m3 < 255)
{
pos = transformVector(pos, m3);
}
}

if(iMatrixChain.y != 0)
{
// unpack packed matrix indicies
int m0 = (iMatrixChain.y & (0xff << 24)) >> 24;
int m1 = (iMatrixChain.y >> 16) & 0xff;
int m2 = (iMatrixChain.y & 0xff00) >> 8;
int m3 = (iMatrixChain.y & 0xff);

if(m0 >=0 && m0 < 255)
{
pos = transformVector(pos, m0);
}

if(m1 >=0 && m1 < 255)
{
pos = transformVector(pos, m1);
}

if(m2 >=0 && m2 < 255)
{
pos = transformVector(pos, m2);
}

if(m3 >=0 && m3 < 255)
{
pos = transformVector(pos, m3);
}
}

if(iMatrixChain.z != 0)
{
// unpack packed matrix indicies
int m0 = (iMatrixChain.z & (0xff << 24)) >> 24;
int m1 = (iMatrixChain.z >> 16) & 0xff;
int m2 = (iMatrixChain.z & 0xff00) >> 8;
int m3 = (iMatrixChain.z & 0xff);

if(m0 >=0 && m0 < 255)
{
pos = transformVector(pos, m0);
}

if(m1 >=0 && m1 < 255)
{
pos = transformVector(pos, m1);
}

if(m2 >=0 && m2 < 255)
// Unpack matrix indices from iMatrixChain (packed as 4 bytes per int component)
// and sequentially transform the vertex position.
for (int i = 0; i < 3; ++i)
{
int chain = iMatrixChain[i];
// Skip empty (0) and default static/unanimated (-1) matrix chain components
if (chain != 0 && chain != -1)
{
pos = transformVector(pos, m2);
// Extract individual matrix index bytes (0-254)
int m0 = (chain >> 24) & 0xff;
int m1 = (chain >> 16) & 0xff;
int m2 = (chain >> 8) & 0xff;
int m3 = chain & 0xff;

// Transform using active bone matrix
if (m0 >= 0 && m0 < 255) pos = transformVector(pos, m0);
if (m1 >= 0 && m1 < 255) pos = transformVector(pos, m1);
if (m2 >= 0 && m2 < 255) pos = transformVector(pos, m2);
if (m3 >= 0 && m3 < 255) pos = transformVector(pos, m3);
}

if(m3 >=0 && m3 < 255)
{
pos = transformVector(pos, m3);
}
}

pos.z = -pos.z;
Expand Down
5 changes: 3 additions & 2 deletions assets/Shaders/picking.frag
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Original file line number Diff line number Diff line change
@@ -1,8 +1,9 @@
#version 150 core
#version 150 core
uniform int uObjectIndex;
out vec4 fragColor;

void main(void)
{
fragColor.r = float(uObjectIndex);
// Write object index to red channel and write 0/1 to other channels to avoid undefined behavior
fragColor = vec4(float(uObjectIndex), 0.0, 0.0, 1.0);
}
46 changes: 14 additions & 32 deletions assets/Shaders/rectangle.vert
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Original file line number Diff line number Diff line change
Expand Up @@ -5,40 +5,22 @@ uniform vec2 uPoint;
uniform vec2 uSize;
uniform vec2 uCoordinates;
out vec2 textureCoord;
vec4 viewPos = vec4(0,0,0,0);

// Offset lookup table to map gl_VertexID to quad corners without branching
const vec2 offsets[6] = vec2[](
vec2(0.0, 0.0), // Top-left
vec2(1.0, 0.0), // Top-right
vec2(1.0, 1.0), // Bottom-right
vec2(0.0, 0.0), // Top-left (second triangle)
vec2(0.0, 1.0), // Bottom-left
vec2(1.0, 1.0) // Bottom-right
);

void main()
{
if(gl_VertexID == 0)
{
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x, uPoint.y, 0), 1.0);
textureCoord = vec2(0,0);
}
else if (gl_VertexID == 1)
{
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x + uSize.x, uPoint.y, 0), 1.0);
textureCoord = vec2(uCoordinates.x,0);
}
else if (gl_VertexID == 2)
{
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x + uSize.x, uPoint.y + uSize.y, 0), 1.0);
textureCoord = uCoordinates;
}
else if (gl_VertexID == 3)
{
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x, uPoint.y, 0), 1.0);
textureCoord = vec2(0,0);
}
else if (gl_VertexID == 4)
{
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x, uPoint.y + uSize.y, 0), 1.0);
textureCoord = vec2(0, uCoordinates.y);
}
else if (gl_VertexID == 5)
{
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x + uSize.x, uPoint.y + uSize.y, 0), 1.0);
textureCoord = uCoordinates;
}

// Calculate vertex position and texture coordinates based on current vertex ID offsets
vec2 offset = offsets[gl_VertexID];
vec4 viewPos = uCurrentModelViewMatrix * vec4(uPoint + offset * uSize, 0.0, 1.0);
textureCoord = offset * uCoordinates;
gl_Position = uCurrentProjectionMatrix * viewPos;
}
55 changes: 19 additions & 36 deletions assets/Shaders/shadow_depth.vert
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Original file line number Diff line number Diff line change
Expand Up @@ -48,43 +48,26 @@ void main()
{
vec3 pos = iPosition;

if(iMatrixChain.x != 0)
{
int m0 = (iMatrixChain.x & (0xff << 24)) >> 24;
int m1 = (iMatrixChain.x >> 16) & 0xff;
int m2 = (iMatrixChain.x & 0xff00) >> 8;
int m3 = (iMatrixChain.x & 0xff);

if(m0 >=0 && m0 < 255) pos = transformVector(pos, m0);
if(m1 >=0 && m1 < 255) pos = transformVector(pos, m1);
if(m2 >=0 && m2 < 255) pos = transformVector(pos, m2);
if(m3 >=0 && m3 < 255) pos = transformVector(pos, m3);
}

if(iMatrixChain.y != 0)
{
int m0 = (iMatrixChain.y & (0xff << 24)) >> 24;
int m1 = (iMatrixChain.y >> 16) & 0xff;
int m2 = (iMatrixChain.y & 0xff00) >> 8;
int m3 = (iMatrixChain.y & 0xff);

if(m0 >=0 && m0 < 255) pos = transformVector(pos, m0);
if(m1 >=0 && m1 < 255) pos = transformVector(pos, m1);
if(m2 >=0 && m2 < 255) pos = transformVector(pos, m2);
if(m3 >=0 && m3 < 255) pos = transformVector(pos, m3);
}
// Unpack matrix indices from iMatrixChain (packed as 4 bytes per int component)
// and sequentially transform the vertex position.
for (int i = 0; i < 3; ++i)
{
int chain = iMatrixChain[i];
// Skip empty (0) and default static/unanimated (-1) matrix chain components
if (chain != 0 && chain != -1)
{
// Extract individual matrix index bytes (0-254)
int m0 = (chain >> 24) & 0xff;
int m1 = (chain >> 16) & 0xff;
int m2 = (chain >> 8) & 0xff;
int m3 = chain & 0xff;

if(iMatrixChain.z != 0)
{
int m0 = (iMatrixChain.z & (0xff << 24)) >> 24;
int m1 = (iMatrixChain.z >> 16) & 0xff;
int m2 = (iMatrixChain.z & 0xff00) >> 8;
int m3 = (iMatrixChain.z & 0xff);

if(m0 >=0 && m0 < 255) pos = transformVector(pos, m0);
if(m1 >=0 && m1 < 255) pos = transformVector(pos, m1);
if(m2 >=0 && m2 < 255) pos = transformVector(pos, m2);
if(m3 >=0 && m3 < 255) pos = transformVector(pos, m3);
// Transform using active bone matrix
if (m0 >= 0 && m0 < 255) pos = transformVector(pos, m0);
if (m1 >= 0 && m1 < 255) pos = transformVector(pos, m1);
if (m2 >= 0 && m2 < 255) pos = transformVector(pos, m2);
if (m3 >= 0 && m3 < 255) pos = transformVector(pos, m3);
}
}

// OpenBVE explicitly negates Z for world geometry.
Expand Down
42 changes: 14 additions & 28 deletions assets/Shaders/text.vert
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Original file line number Diff line number Diff line change
Expand Up @@ -6,36 +6,22 @@ uniform vec2 uPoint;
uniform vec2 uSize;
uniform vec4 uAtlasLocation;
out vec2 textureCoord;
vec4 viewPos = vec4(0,0,0,0);

// Offset lookup table to map gl_VertexID to quad corners without branching
const vec2 offsets[6] = vec2[](
vec2(0.0, 0.0), // Top-left
vec2(1.0, 0.0), // Top-right
vec2(1.0, 1.0), // Bottom-right
vec2(0.0, 0.0), // Top-left (second triangle)
vec2(0.0, 1.0), // Bottom-left
vec2(1.0, 1.0) // Bottom-right
);

void main()
{
switch(gl_VertexID)
{
case 0:
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x, uPoint.y, 0), 1.0);
textureCoord = vec2(uAtlasLocation.x, uAtlasLocation.y);
break;
case 1:
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x + uSize.x, uPoint.y, 0), 1.0);
textureCoord = vec2(uAtlasLocation.x + uAtlasLocation.z, uAtlasLocation.y);
break;
case 2:
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x + uSize.x, uPoint.y + uSize.y, 0), 1.0);
textureCoord = vec2(uAtlasLocation.x + uAtlasLocation.z, uAtlasLocation.y + uAtlasLocation.w);
break;
case 3:
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x, uPoint.y, 0), 1.0);
textureCoord = vec2(uAtlasLocation.x, uAtlasLocation.y);
break;
case 4:
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x, uPoint.y + uSize.y, 0), 1.0);
textureCoord = vec2(uAtlasLocation.x, uAtlasLocation.y + uAtlasLocation.w);
break;
case 5:
viewPos = uCurrentModelViewMatrix * vec4(vec3(uPoint.x + uSize.x, uPoint.y + uSize.y, 0), 1.0);
textureCoord = vec2(uAtlasLocation.x + uAtlasLocation.z, uAtlasLocation.y + uAtlasLocation.w);
break;
}
// Calculate vertex position and UVs from atlas location using lookup offsets
vec2 offset = offsets[gl_VertexID];
vec4 viewPos = uCurrentModelViewMatrix * vec4(uPoint + offset * uSize, 0.0, 1.0);
textureCoord = uAtlasLocation.xy + offset * uAtlasLocation.zw;
gl_Position = uCurrentProjectionMatrix * viewPos;
}