Single channel should show as black and white in viewport #2952
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A single channel image would show as red/black when used in a RGB context. Make sure those images show a black and white.
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Created test textures in 16/32 bit EXR with either Mono or Mono+Alpha channels to exercise all conversions.
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Tests all possible Mono and Mono+Alpha precisions.
| { | ||
| uniform token info:id = "ND_image_color3" | ||
| asset inputs:file = @textures/R8U.png@ | ||
| color3f outputs:out |
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Even though the texture is single channel, we use it in a color3 context and expect black&white results.
| for (int y = 0; y < spec.height; y++) { | ||
| for (int x = 0; x < spec.width; x++) { | ||
| const int t = spec.width * y + x; | ||
| for (int b = 0; b < bpp_RGB32; b++) { |
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This is a time-critical cycle. Do we want to multithread it or optimize otherwise?
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Texture loading is already done on a separate thread, so basically out of the critical path for MayaUSD. I can try to make sure the code is optimal though. A first look at the dissassembly showed that the compiler was unsure if the previous write did not overlap the read and was forced to re-read the source value.
Help the compiler by making sure that reading the source buffer is done only once. Without that, the compiler has to consider that every read could be on a buffer modified by the previous write (e.g. not allowed to know the buffers do not overlap).
| for (int b = 0; b < bpp_RGB32; b++) { | ||
| texels[t * bpp_RGB32 + b] = storage[t * bpp + (b % 4)]; | ||
| for (int b = 0; b < bits_RGB32; b++) { | ||
| const unsigned char bits = storage[t * bpp + b]; |
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Read the source buffer only once.
Prevents recomputing adresses and generates the most optimal assembly code so far.
Most likely to fail on mismatched variable sizes.
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@seando-adsk ready for merge. Thanks! |
A single channel image would show as red/black when used in a RGB context. Make sure those images show a black and white.