I’ve made some progress on this in that I understand Urho3D only supports one color per vertex, whereas I need three colors per vertex (sun, torch and anti-light). I decided to make some experimental changes to a copy of Urho3D source code to see if I could get it to support multiple colors per vertex with vertex buffers.
What I’m looking for is feedback as to whether I’m going down the right path or not.
Here’s what I changed in a copy of Urho3D source code:
diff -r -U3 /tmp/Urho3D-master/Source/Urho3D/Graphics/GraphicsDefs.cpp ./Source/Urho3D/Graphics/GraphicsDefs.cpp
--- /tmp/Urho3D-master/Source/Urho3D/Graphics/GraphicsDefs.cpp 2020-07-27 06:31:27.000000000 -0700
+++ ./Source/Urho3D/Graphics/GraphicsDefs.cpp 2020-10-04 16:01:29.154308332 -0700
@@ -97,6 +97,8 @@
VertexElement(TYPE_VECTOR3, SEM_POSITION, 0, false), // Position
VertexElement(TYPE_VECTOR3, SEM_NORMAL, 0, false), // Normal
VertexElement(TYPE_UBYTE4_NORM, SEM_COLOR, 0, false), // Color
+ VertexElement(TYPE_UBYTE4_NORM, SEM_COLOR, 0, false), // Color2
+ VertexElement(TYPE_UBYTE4_NORM, SEM_COLOR, 0, false), // Color3
VertexElement(TYPE_VECTOR2, SEM_TEXCOORD, 0, false), // Texcoord1
VertexElement(TYPE_VECTOR2, SEM_TEXCOORD, 1, false), // Texcoord2
VertexElement(TYPE_VECTOR3, SEM_TEXCOORD, 0, false), // Cubetexcoord1
diff -r -U3 /tmp/Urho3D-master/Source/Urho3D/Graphics/GraphicsDefs.h ./Source/Urho3D/Graphics/GraphicsDefs.h
--- /tmp/Urho3D-master/Source/Urho3D/Graphics/GraphicsDefs.h 2020-07-27 06:31:27.000000000 -0700
+++ ./Source/Urho3D/Graphics/GraphicsDefs.h 2020-10-04 14:23:35.474301914 -0700
@@ -136,6 +136,8 @@
ELEMENT_POSITION = 0,
ELEMENT_NORMAL,
ELEMENT_COLOR,
+ ELEMENT_COLOR2,
+ ELEMENT_COLOR3,
ELEMENT_TEXCOORD1,
ELEMENT_TEXCOORD2,
ELEMENT_CUBETEXCOORD1,
@@ -452,21 +454,23 @@
// Legacy vertex element bitmasks.
enum VertexMask : unsigned
{
- MASK_NONE = 0x0,
- MASK_POSITION = 0x1,
- MASK_NORMAL = 0x2,
- MASK_COLOR = 0x4,
- MASK_TEXCOORD1 = 0x8,
- MASK_TEXCOORD2 = 0x10,
- MASK_CUBETEXCOORD1 = 0x20,
- MASK_CUBETEXCOORD2 = 0x40,
- MASK_TANGENT = 0x80,
- MASK_BLENDWEIGHTS = 0x100,
- MASK_BLENDINDICES = 0x200,
- MASK_INSTANCEMATRIX1 = 0x400,
- MASK_INSTANCEMATRIX2 = 0x800,
- MASK_INSTANCEMATRIX3 = 0x1000,
- MASK_OBJECTINDEX = 0x2000,
+ MASK_NONE = 0x0000,
+ MASK_POSITION = 0x0001,
+ MASK_NORMAL = 0x0002,
+ MASK_COLOR = 0x0004,
+ MASK_COLOR2 = 0x0008,
+ MASK_COLOR3 = 0x0010,
+ MASK_TEXCOORD1 = 0x0020,
+ MASK_TEXCOORD2 = 0x0040,
+ MASK_CUBETEXCOORD1 = 0x0080,
+ MASK_CUBETEXCOORD2 = 0x0100,
+ MASK_TANGENT = 0x0200,
+ MASK_BLENDWEIGHTS = 0x0400,
+ MASK_BLENDINDICES = 0x0800,
+ MASK_INSTANCEMATRIX1 = 0x1000,
+ MASK_INSTANCEMATRIX2 = 0x2000,
+ MASK_INSTANCEMATRIX3 = 0x4000,
+ MASK_OBJECTINDEX = 0x8000
};
URHO3D_FLAGSET(VertexMask, VertexMaskFlags);
In a copy of bin/CoreData/Shaders/GLSL/Transform.glsl called TransformC3.glsl, I’ve done this:
--- bin/CoreData/Shaders/GLSL/Transform.glsl 2018-10-28 08:20:42.000000000 -0700
+++ bin/CoreData/Shaders/GLSL/TransformC3.glsl 2020-10-04 14:28:03.170968864 -0700
@@ -9,6 +9,8 @@
attribute vec4 iPos;
attribute vec3 iNormal;
attribute vec4 iColor;
+attribute vec4 iColor2;
+attribute vec4 iColor3;
attribute vec2 iTexCoord;
attribute vec2 iTexCoord1;
attribute vec4 iTangent;
In a copy of bin/CoreData/Shaders/GLSL/Unlit.glsl called UnlitC3.glsl, I’ve done this:
--- bin/CoreData/Shaders/GLSL/Unlit.glsl 2018-10-28 08:20:42.000000000 -0700
+++ bin/CoreData/Shaders/GLSL/UnlitC3.glsl 2020-10-04 17:24:30.407646913 -0700
@@ -1,6 +1,6 @@
#include "Uniforms.glsl"
#include "Samplers.glsl"
-#include "Transform.glsl"
+#include "TransformC3.glsl"
#include "ScreenPos.glsl"
#include "Fog.glsl"
@@ -8,6 +8,8 @@
varying vec4 vWorldPos;
#ifdef VERTEXCOLOR
varying vec4 vColor;
+ varying vec4 vColor2;
+ varying vec4 vColor3;
#endif
void VS()
@@ -20,8 +22,9 @@
#ifdef VERTEXCOLOR
vColor = iColor;
+ vColor2 = iColor2;
+ vColor3 = iColor3;
#endif
-
}
void PS()
@@ -38,6 +41,7 @@
#endif
#ifdef VERTEXCOLOR
+ // mix together multiple colors here
diffColor *= vColor;
#endif
I’ve defined a technique called DiffUnlitVCol3.xml as follows which utilizes the shader:
<technique vs="UnlitC3" ps="UnlitC3" vsdefines="VERTEXCOLOR" psdefines="DIFFMAP VERTEXCOLOR">
<pass name="base" />
</technique>
And a material called VoxelsAtlas.xml which utilizes the technique:
<material>
<technique name="Techniques/DiffUnlitVCol3.xml" />
<texture unit="diffuse" name="Textures/VoxelsAtlas.dds" />
</material>
In my C++ application code I create a model using a vertex buffer with three colors per vertex and add it as a node to the scene. In the PS function, in the shader UnlitC3.glsl, if I code “diffColor *= vColor;” I get what I would expect, but if I instead use “diffColor *= vColor2;” I get results which look like vec4 colors that are uninitialized (mainly the color black with some weird colors here and there). I’ve verified the vertex buffer data is being filled in correctly on the application side, so I’m unsure what I’m most likely doing wrong in the Urho3D code changes.
