Based on SIGGRAPH2007_EfficientSelfShadowedRadiosityNormalMapping.pdf
The geometry is rendered 3 times with alpha blending enabled to achieve normalmapping. Original paper uses 3-pass additive blending, but it can be replaced with alpha blending.
Two 32-color textures with 3-bit alpha are used for rendering. (First texture is used twice with alpha blending disabled on the first rendering pass and enabled on the second)
