我有一个与 XNA 一起使用的像素着色器（如下）。在我的笔记本电脑（蹩脚的显卡）上，它运行起来有点生涩，但还可以。我刚刚尝试在 xbox 上运行它，这太可怕了！
游戏没有任何内容（它只是一个分形渲染器），所以它必须是导致问题的像素着色器。我也认为这是 PS 代码，因为我降低了迭代次数，没关系。我也检查过，GC delta 为零。
xbox 上是否有任何禁止使用的 HLSL 功能？我一定是在这里做错了，性能不会那么差！
#include "FractalBase.fxh"
float ZPower;
float3 Colour;
float3 ColourScale;
float ComAbs(float2 Arg)
{
return sqrt(Arg.x * Arg.x + Arg.y * Arg.y);
}
float2 ComPow(float2 Arg, float Power)
{
float Mod = pow(Arg.x * Arg.x + Arg.y * Arg.y, Power / 2);
float Ang = atan2(Arg.y, Arg.x) * Power;
return float2(Mod * cos(Ang), Mod * sin(Ang));
}
float4 FractalPixelShader(float2 texCoord : TEXCOORD0, uniform float Iterations) : COLOR0
{
float2 c = texCoord.xy;
float2 z = 0;
float i;
float oldBailoutTest = 0;
float bailoutTest = 0;
for(i = 0; i < Iterations; i++)
{
z = ComPow(z, ZPower) + c;
bailoutTest = z.x * z.x + z.y * z.y;
if(bailoutTest >= ZPower * ZPower)
{
break;
}
oldBailoutTest = bailoutTest;
}
float normalisedIterations = i / Iterations;
float factor = (bailoutTest - oldBailoutTest) / (ZPower * ZPower - oldBailoutTest);
float4 Result = normalisedIterations + (1 / factor / Iterations);
Result = (i >= Iterations - 1) ? float4(0.0, 0.0, 0.0, 1.0) : float4(Result.x * Colour.r * ColourScale.x, Result.y * Colour.g * ColourScale.y, Result.z * Colour.b * ColourScale.z, 1);
return Result;
}
technique Technique1
{
pass
{
VertexShader = compile vs_3_0 SpriteVertexShader();
PixelShader = compile ps_3_0 FractalPixelShader(128);
}
}
下面是 FractalBase.fxh：
float4x4 MatrixTransform : register(vs, c0);
float2 Pan;
float Zoom;
float Aspect;
void SpriteVertexShader(inout float4 Colour : COLOR0,
inout float2 texCoord : TEXCOORD0,
inout float4 position : SV_Position)
{
position = mul(position, MatrixTransform);
// Convert the position into from screen space into complex coordinates
texCoord = (position) * Zoom * float2(1, Aspect) - float2(Pan.x, -Pan.y);
}
编辑我确实尝试通过使用大量 lerps 来删除条件，但是当我这样做时，我得到了大量的文物（而不是“属于博物馆”的那种！）。我改变了一些东西，并修复了一些逻辑错误，但关键是将 GreaterThan 结果乘以 1 + epsilon，以解决舍入误差仅使 0.9999 = 0（整数）。请参阅下面的固定代码：
#include "FractalBase.fxh"
float ZPower;
float3 Colour;
float3 ColourScale;
float ComAbs(float2 Arg)
{
return sqrt(Arg.x * Arg.x + Arg.y * Arg.y);
}
float2 ComPow(float2 Arg, float Power)
{
float Mod = pow(Arg.x * Arg.x + Arg.y * Arg.y, Power / 2);
float Ang = atan2(Arg.y, Arg.x) * Power;
return float2(Mod * cos(Ang), Mod * sin(Ang));
}
float GreaterThan(float x, float y)
{
return ((x - y) / (2 * abs(x - y)) + 0.5) * 1.001;
}
float4 FractalPixelShader(float2 texCoord : TEXCOORD0, uniform float Iterations) : COLOR0
{
float2 c = texCoord.xy;
float2 z = 0;
int i;
float oldBailoutTest = 0;
float bailoutTest = 0;
int KeepGoing = 1;
int DoneIterations = Iterations;
int Bailout = 0;
for(i = 0; i < Iterations; i++)
{
z = lerp(z, ComPow(z, ZPower) + c, KeepGoing);
bailoutTest = lerp(bailoutTest, z.x * z.x + z.y * z.y, KeepGoing);
Bailout = lerp(Bailout, GreaterThan(bailoutTest, ZPower * ZPower), -abs(Bailout) + 1);
KeepGoing = lerp(KeepGoing, 0.0, Bailout);
DoneIterations = lerp(DoneIterations, min(i, DoneIterations), Bailout);
oldBailoutTest = lerp(oldBailoutTest, bailoutTest, KeepGoing);
}
float normalisedIterations = DoneIterations / Iterations;
float factor = (bailoutTest - oldBailoutTest) / (ZPower * ZPower - oldBailoutTest);
float4 Result = normalisedIterations + (1 / factor / Iterations);
Result = (DoneIterations >= Iterations - 1) ? float4(0.0, 0.0, 0.0, 1.0) : float4(Result.x * Colour.r * ColourScale.x, Result.y * Colour.g * ColourScale.y, Result.z * Colour.b * ColourScale.z, 1);
return Result;
}
technique Technique1
{
pass
{
VertexShader = compile vs_3_0 SpriteVertexShader();
PixelShader = compile ps_3_0 FractalPixelShader(128);
}
}