Support any texture with interpolate scalars

LucasGandel · LucasGandel · commit 79969286ea2d · 2023-06-09T13:47:54.000+02:00
VTK !8186 added support for using multitexturing with
InterpolateScalarsBeforeMappingOn to allow for blending interpolated
scalars with texture coloring.
This commit extends this support to the "actortexture" and "albedoTex"
textures that can be respectively set with vtkActor::SetTexture() and
vtkActor::GetProperty()-&gt;SetBaseColorTexture().

When turning on InterpolateScalarsBeforeMapping, the mapper internally
creates a texture with the associated texture coordinates.
This commit adds a specific attribute for those tcoords to avoid overriding
the existing polydata tcoords.
diff --git a/Rendering/OpenGL2/vtkOpenGLPolyDataMapper.cxx b/Rendering/OpenGL2/vtkOpenGLPolyDataMapper.cxx
@@ -422,6 +422,13 @@ std::string vtkOpenGLPolyDataMapper::GetTextureCoordinateName(const char* tname)
       return it.first;
     }
   }
+
+  // Return the attribute name of the specific tcoords used for scalar coloring with texture
+  if (tname == std::string("colortexture"))
+  {
+    return "colorTCoord";
+  }
+
   return std::string("tcoord");
 }
 
@@ -473,8 +480,7 @@ std::vector<texinfo> vtkOpenGLPolyDataMapper::GetTextures(vtkActor* actor)
 //------------------------------------------------------------------------------
 bool vtkOpenGLPolyDataMapper::HaveTCoords(vtkPolyData* poly)
 {
-  return (
-    this->ColorCoordinates || poly->GetPointData()->GetTCoords() || this->ForceTextureCoordinates);
+  return (poly->GetPointData()->GetTCoords() || this->ForceTextureCoordinates);
 }
 
 //------------------------------------------------------------------------------
@@ -736,7 +742,7 @@ void vtkOpenGLPolyDataMapper::ReplaceShaderColor(
   else if (this->InterpolateScalarsBeforeMapping && this->ColorCoordinates &&
     !this->DrawingVertices)
   {
-    colorImpl += "  vec4 texColor = texture(colortexture, tcoordVCVSOutput.st);\n"
+    colorImpl += "  vec4 texColor = texture(colortexture, colorTCoordVCVSOutput.st);\n"
                  "  vec3 ambientColor = ambientIntensity * texColor.rgb;\n"
                  "  vec3 diffuseColor = diffuseIntensity * texColor.rgb;\n"
                  "  float opacity = opacityUniform * texColor.a;";
@@ -3899,19 +3905,18 @@ void vtkOpenGLPolyDataMapper::BuildBufferObjects(vtkRenderer* ren, vtkActor* act
   // if we have offsets from the cell map then use them
   this->CellCellMap->BuildPrimitiveOffsetsIfNeeded(prims, representation, poly->GetPoints());
 
-  // Set the texture if we are going to use texture
-  // for coloring with a point attribute.
+  // Set the texture coordinate attribute if we are going to use texture for coloring
   vtkDataArray* tcoords = nullptr;
   if (this->HaveTCoords(poly))
   {
-    if (this->InterpolateScalarsBeforeMapping && this->ColorCoordinates)
-    {
-      tcoords = this->ColorCoordinates;
-    }
-    else
-    {
-      tcoords = poly->GetPointData()->GetTCoords();
-    }
+    tcoords = poly->GetPointData()->GetTCoords();
+  }
+
+  // Set specific texture coordinates if we are going to use texture for scalar coloring
+  vtkDataArray* colorTCoords = nullptr;
+  if (this->InterpolateScalarsBeforeMapping && this->ColorCoordinates)
+  {
+    colorTCoords = this->ColorCoordinates;
   }
 
   vtkOpenGLRenderWindow* renWin = vtkOpenGLRenderWindow::SafeDownCast(ren->GetRenderWindow());
@@ -3937,6 +3942,7 @@ void vtkOpenGLPolyDataMapper::BuildBufferObjects(vtkRenderer* ren, vtkActor* act
   this->VBOs->CacheDataArray("normalMC", n, cache, VTK_FLOAT);
   this->VBOs->CacheDataArray("scalarColor", c, cache, VTK_UNSIGNED_CHAR);
   this->VBOs->CacheDataArray("tcoord", tcoords, cache, VTK_FLOAT);
+  this->VBOs->CacheDataArray("colorTCoord", colorTCoords, cache, VTK_FLOAT);
 
   // Look for tangents attribute
   vtkFloatArray* tangents = vtkFloatArray::SafeDownCast(poly->GetPointData()->GetTangents());
