koobas.hobune.stream
Using SetPixel in Update()
I've been working on making a perlin procedural texture generator, and I have come to a strange dilema. I cannot seem to use the SetPixel function within the Update function. When using SetPixel in awake it works, but I need to be able to change my textures pixels in real time.
My awake function
function Awake(){
colors = new Array(16384);
texture = new Texture2D(128, 128);
renderer.material.mainTexture = texture;
// Fill the texture with Sierpinski's fractal pattern!
for (var y : int = 0; y < texture.height; ++y) {
for (var x : int = 0; x < texture.width; ++x) {
setTex(x, y);
}
}
// Apply all SetPixel calls
texture.Apply();
//setTex();
}
What does not work mean? The above code is likely to drag your frame rate way down. Is that what you mean?
Originally, nothing would happen at all. But now it does just as you said, it drags the frame rate way down.
You can improve the performance by using Texture2D.GetPixels() and Texture2D.SetPixels(). Better yet use Texture2D.GetPixels32() and Texture2D.SetPixels32(). Using these routines, you extract all the pixels from the texture, make your changes, and then insert you changes back into the texture. Avoid making function calls in the inner loop of your routine.
I fear even the optimizations proposed by @robertbu in the comments above might not help much. I think the performance hit is more likely to come from transferring the texture from main memory to the graphics card than from a pixel operation on the CPU, i.e. it's the call to texture.Apply() that kills your frame rate. Unfortunately, the PCI bus is always going to be a lot slower than computing things on either the GPU or the CPU.
I'm sorry to say that the only way to efficiently make real-time changes to a texture is to render them to a RenderTexture on the graphics card itself, since this avoids the expensive transfer. This is a Unity Pro feature, so if you're on the free version, you're out of luck. Unless some wizard pops by who has a brilliant solution, in which case I will follow this post closely. ;-)
I just ran a quick test of SetPixels32() vs SetPixel(). I don't know what hardware the OP is testing on. Using my desktop and running the app in the editor, I saw no FPS slowdown with a 128 x 128 image. I saw a bit of slowdown with the SetPixel() version at 512 x 512 with an FPS of 68 vs 61. The real big hit came at 1024 x 1024. with an FPS of 40 vs 6. These numbers make me wonder if the OPs slowdown had more to do with whatever calculates he was doing inside of setTex() and less to do with SetPixel().
