Hi,
Is there a way to specify the blending mode of symbols drawn on a layer? Something equivalent to
- GL_FUNC_ADD: The source and destination colors are added to each other. O = sS + dD. The The s and d are blending parameters that are multiplied into each of S and D before the addition.
- GL_FUNC_SUBTRACT: Subtracts the destination from the source. O = sS - dD. The source and dest are multiplied by blending parameters.
- GL_FUNC_REVERSE_SUBTRACT: Subtracts the source from the destination. O = dD - sS. The source and dest are multiplied by blending parameters.
- GL_MIN: The output color is the component-wise minimum value of the source and dest colors. So performing GL_MIN in the RGB equation means that Or = min(Sr, Dr), Og = min(Sg, Dg), and so forth. The parameters s and d are ignored for this equation.
- GL_MAX: The output color is the component-wise maximum value of the source and dest colors. The parameters s and d are ignored for this equation.
I'd like to sum the shades of grey of two symbols overlapping, and then specify a colormapping mode for rendering the layer.
