|
|
| Reporter | SteveL | Assigned To | SteveL | |
|---|
| Priority | normal | Severity | normal | Reproducibility | N/A |
|---|
| Status | closed | Resolution | no change required | |
|---|
| Product Version | TDM 2.03 | |
|---|
|
|
| Summary | 0003883: Post processing shaders doing more sums than needed |
|---|
| Description | From a note on issue 0003877
On the environmental variables: shaders that use _currentRender do unnecessary work. The _currentRender capture in the renderer c++ code sets environmental constants for both the screen size and the power-of-two texture size, to allow shaders to translate a screen position to a texture coordinate. But when you lay out the math, only the reciprocal of the power-of-two texture size is really needed to do that. The screen size cancels out in the algebra. That's how I did it in the "depth window" shader and video I posted in the engine thread. I'll add a new environmental constant for depth-capture-related fragment programs which holds that reciprocal, and maybe open another tracker to change the shaders using _currentRender if it turns out that they're doing that extra calculation for every pixel instead of just once (I don't have the code in front of me right now). |
|---|
| Additional Information | The calculation *is* done for each fragment, at least in HeatHaze.vfp, and lots (or maybe all) other PP shaders copy from it.
Actions required:
- Check whether the simple reciprocal does indeed cover all possible permutations of screen and texture size
- See whether this makes any performance difference and decide whether it's worth fixing. |
|---|
| Tags | No tags attached. |
|---|
|
|
