For reference, I’m working from this manual page.
Looking at the manual, it indicates that the “interpolate” combine mode uses its third source to interpolate between its first two sources.
In your case, those first two sources would be your two textures–one coming from the previous texture-stage, and one set on the current texture-stage (i.e. the one that uses the “interpolate” mode).
Since you want to blend the colours of your textures (if I have it correctly), your operands would indicate that the texture-stage should fetch colours.
Now, you want to be able to vary the value used for interpolation (that is, the one given as the third source). Thus you probably don’t want to use a texture here. (I daresay that you could, but that seems like an awkward way to do it, it seems to me.)
Looking at the list of available sources given in the manual, two look promising: “TextureStage.CSConstant”, which uses the value set in “TextureStage.setColor”, and “TextureStage.CSConstantColorScale”, which uses the value set in “NodePath.setColorScale”. Either way, this source provides a constant colour that you can alter in code.
I’ve chosen “CSConstant” below, but either should work–go with whichever you prefer, I think.
Thus, if I’m not much mistaken:
- Your first two sources would be the previous texture and the current texture (and thus “TextureStage.CSPrevious” and “TextureStage.CSTexture”, respectively)
- Your operands would all be simply the colour of their respective sources (“TextureStage.COSrcColor”)
- The final source, which is used to select between the first two sources, would be a constant value, applied via “TextureStage.setColor” (“TextureStage.CSConstant”)