我需要帮助优化以下一组着色器：
顶点：
precision mediump float;
uniform vec2 rubyTextureSize;
attribute vec4 vPosition;
attribute vec2 a_TexCoordinate;
varying vec2 tc;
void main() {
gl_Position = vPosition;
tc = a_TexCoordinate;
}
分段：
precision mediump float;
/*
Uniforms
- rubyTexture: texture sampler
- rubyTextureSize: size of the texture before rendering
*/
uniform sampler2D rubyTexture;
uniform vec2 rubyTextureSize;
uniform vec2 rubyTextureFract;
/*
Varying attributes
- tc: coordinate of the texel being processed
- xyp_[]_[]_[]: a packed coordinate for 3 areas within the texture
*/
varying vec2 tc;
/*
Constants
*/
/*
Inequation coefficients for interpolation
Equations are in the form: Ay + Bx = C
45, 30, and 60 denote the angle from x each line the cooeficient variable set builds
*/
const vec4 Ai = vec4(1.0, -1.0, -1.0, 1.0);
const vec4 B45 = vec4(1.0, 1.0, -1.0, -1.0);
const vec4 C45 = vec4(1.5, 0.5, -0.5, 0.5);
const vec4 B30 = vec4(0.5, 2.0, -0.5, -2.0);
const vec4 C30 = vec4(1.0, 1.0, -0.5, 0.0);
const vec4 B60 = vec4(2.0, 0.5, -2.0, -0.5);
const vec4 C60 = vec4(2.0, 0.0, -1.0, 0.5);
const vec4 M45 = vec4(0.4, 0.4, 0.4, 0.4);
const vec4 M30 = vec4(0.2, 0.4, 0.2, 0.4);
const vec4 M60 = M30.yxwz;
const vec4 Mshift = vec4(0.2);
// Coefficient for weighted edge detection
const float coef = 2.0;
// Threshold for if luminance values are "equal"
const vec4 threshold = vec4(0.32);
// Conversion from RGB to Luminance (from GIMP)
const vec3 lum = vec3(0.21, 0.72, 0.07);
// Performs same logic operation as && for vectors
bvec4 _and_(bvec4 A, bvec4 B) {
return bvec4(A.x && B.x, A.y && B.y, A.z && B.z, A.w && B.w);
}
// Performs same logic operation as || for vectors
bvec4 _or_(bvec4 A, bvec4 B) {
return bvec4(A.x || B.x, A.y || B.y, A.z || B.z, A.w || B.w);
}
// Converts 4 3-color vectors into 1 4-value luminance vector
vec4 lum_to(vec3 v0, vec3 v1, vec3 v2, vec3 v3) {
// return vec4(dot(lum, v0), dot(lum, v1), dot(lum, v2), dot(lum, v3));
return mat4(v0.x, v1.x, v2.x, v3.x, v0.y, v1.y, v2.y, v3.y, v0.z, v1.z,
v2.z, v3.z, 0.0, 0.0, 0.0, 0.0) * vec4(lum, 0.0);
}
// Gets the difference between 2 4-value luminance vectors
vec4 lum_df(vec4 A, vec4 B) {
return abs(A - B);
}
// Determines if 2 4-value luminance vectors are "equal" based on threshold
bvec4 lum_eq(vec4 A, vec4 B) {
return lessThan(lum_df(A, B), threshold);
}
vec4 lum_wd(vec4 a, vec4 b, vec4 c, vec4 d, vec4 e, vec4 f, vec4 g, vec4 h) {
return lum_df(a, b) + lum_df(a, c) + lum_df(d, e) + lum_df(d, f)
+ 4.0 * lum_df(g, h);
}
// Gets the difference between 2 3-value rgb colors
float c_df(vec3 c1, vec3 c2) {
vec3 df = abs(c1 - c2);
return df.r + df.g + df.b;
}
void main() {
/*
Mask for algorhithm
+-----+-----+-----+-----+-----+
| | 1 | 2 | 3 | |
+-----+-----+-----+-----+-----+
| 5 | 6 | 7 | 8 | 9 |
+-----+-----+-----+-----+-----+
| 10 | 11 | 12 | 13 | 14 |
+-----+-----+-----+-----+-----+
| 15 | 16 | 17 | 18 | 19 |
+-----+-----+-----+-----+-----+
| | 21 | 22 | 23 | |
+-----+-----+-----+-----+-----+
*/
float x = rubyTextureFract.x;
float y = rubyTextureFract.y;
vec4 xyp_1_2_3 = tc.xxxy + vec4(-x, 0.0, x, -2.0 * y);
vec4 xyp_6_7_8 = tc.xxxy + vec4(-x, 0.0, x, -y);
vec4 xyp_11_12_13 = tc.xxxy + vec4(-x, 0.0, x, 0.0);
vec4 xyp_16_17_18 = tc.xxxy + vec4(-x, 0.0, x, y);
vec4 xyp_21_22_23 = tc.xxxy + vec4(-x, 0.0, x, 2.0 * y);
vec4 xyp_5_10_15 = tc.xyyy + vec4(-2.0 * x, -y, 0.0, y);
vec4 xyp_9_14_9 = tc.xyyy + vec4(2.0 * x, -y, 0.0, y);
// Get mask values by performing texture lookup with the uniform sampler
vec3 P1 = texture2D(rubyTexture, xyp_1_2_3.xw).rgb;
vec3 P2 = texture2D(rubyTexture, xyp_1_2_3.yw).rgb;
vec3 P3 = texture2D(rubyTexture, xyp_1_2_3.zw).rgb;
vec3 P6 = texture2D(rubyTexture, xyp_6_7_8.xw).rgb;
vec3 P7 = texture2D(rubyTexture, xyp_6_7_8.yw).rgb;
vec3 P8 = texture2D(rubyTexture, xyp_6_7_8.zw).rgb;
vec3 P11 = texture2D(rubyTexture, xyp_11_12_13.xw).rgb;
vec3 P12 = texture2D(rubyTexture, xyp_11_12_13.yw).rgb;
vec3 P13 = texture2D(rubyTexture, xyp_11_12_13.zw).rgb;
vec3 P16 = texture2D(rubyTexture, xyp_16_17_18.xw).rgb;
vec3 P17 = texture2D(rubyTexture, xyp_16_17_18.yw).rgb;
vec3 P18 = texture2D(rubyTexture, xyp_16_17_18.zw).rgb;
vec3 P21 = texture2D(rubyTexture, xyp_21_22_23.xw).rgb;
vec3 P22 = texture2D(rubyTexture, xyp_21_22_23.yw).rgb;
vec3 P23 = texture2D(rubyTexture, xyp_21_22_23.zw).rgb;
vec3 P5 = texture2D(rubyTexture, xyp_5_10_15.xy).rgb;
vec3 P10 = texture2D(rubyTexture, xyp_5_10_15.xz).rgb;
vec3 P15 = texture2D(rubyTexture, xyp_5_10_15.xw).rgb;
vec3 P9 = texture2D(rubyTexture, xyp_9_14_9.xy).rgb;
vec3 P14 = texture2D(rubyTexture, xyp_9_14_9.xz).rgb;
vec3 P19 = texture2D(rubyTexture, xyp_9_14_9.xw).rgb;
// Store luminance values of each point in groups of 4
// so that we may operate on all four corners at once
vec4 p7 = lum_to(P7, P11, P17, P13);
vec4 p8 = lum_to(P8, P6, P16, P18);
vec4 p11 = p7.yzwx; // P11, P17, P13, P7
vec4 p12 = lum_to(P12, P12, P12, P12);
vec4 p13 = p7.wxyz; // P13, P7, P11, P17
vec4 p14 = lum_to(P14, P2, P10, P22);
vec4 p16 = p8.zwxy; // P16, P18, P8, P6
vec4 p17 = p7.zwxy; // P17, P13, P7, P11
vec4 p18 = p8.wxyz; // P18, P8, P6, P16
vec4 p19 = lum_to(P19, P3, P5, P21);
vec4 p22 = p14.wxyz; // P22, P14, P2, P10
vec4 p23 = lum_to(P23, P9, P1, P15);
// Scale current texel coordinate to [0..1]
vec2 fp = fract(tc * rubyTextureSize);
// Determine amount of "smoothing" or mixing that could be done on texel corners
vec4 AiMulFpy = Ai * fp.y;
vec4 B45MulFpx = B45 * fp.x;
vec4 ma45 = smoothstep(C45 - M45, C45 + M45, AiMulFpy + B45MulFpx);
vec4 ma30 = smoothstep(C30 - M30, C30 + M30, AiMulFpy + B30 * fp.x);
vec4 ma60 = smoothstep(C60 - M60, C60 + M60, AiMulFpy + B60 * fp.x);
vec4 marn = smoothstep(C45 - M45 + Mshift, C45 + M45 + Mshift,
AiMulFpy + B45MulFpx);
// Perform edge weight calculations
vec4 e45 = lum_wd(p12, p8, p16, p18, p22, p14, p17, p13);
vec4 econt = lum_wd(p17, p11, p23, p13, p7, p19, p12, p18);
vec4 e30 = lum_df(p13, p16);
vec4 e60 = lum_df(p8, p17);
// Calculate rule results for interpolation
bvec4 r45_1 = _and_(notEqual(p12, p13), notEqual(p12, p17));
bvec4 r45_2 = _and_(not (lum_eq(p13, p7)), not (lum_eq(p13, p8)));
bvec4 r45_3 = _and_(not (lum_eq(p17, p11)), not (lum_eq(p17, p16)));
bvec4 r45_4_1 = _and_(not (lum_eq(p13, p14)), not (lum_eq(p13, p19)));
bvec4 r45_4_2 = _and_(not (lum_eq(p17, p22)), not (lum_eq(p17, p23)));
bvec4 r45_4 = _and_(lum_eq(p12, p18), _or_(r45_4_1, r45_4_2));
bvec4 r45_5 = _or_(lum_eq(p12, p16), lum_eq(p12, p8));
bvec4 r45 = _and_(r45_1, _or_(_or_(_or_(r45_2, r45_3), r45_4), r45_5));
bvec4 r30 = _and_(notEqual(p12, p16), notEqual(p11, p16));
bvec4 r60 = _and_(notEqual(p12, p8), notEqual(p7, p8));
// Combine rules with edge weights
bvec4 edr45 = _and_(lessThan(e45, econt), r45);
bvec4 edrrn = lessThanEqual(e45, econt);
bvec4 edr30 = _and_(lessThanEqual(coef * e30, e60), r30);
bvec4 edr60 = _and_(lessThanEqual(coef * e60, e30), r60);
// Finalize interpolation rules and cast to float (0.0 for false, 1.0 for true)
vec4 final45 = vec4(_and_(_and_(not (edr30), not (edr60)), edr45));
vec4 final30 = vec4(_and_(_and_(edr45, not (edr60)), edr30));
vec4 final60 = vec4(_and_(_and_(edr45, not (edr30)), edr60));
vec4 final36 = vec4(_and_(_and_(edr60, edr30), edr45));
vec4 finalrn = vec4(_and_(not (edr45), edrrn));
// Determine the color to mix with for each corner
vec4 px = step(lum_df(p12, p17), lum_df(p12, p13));
// Determine the mix amounts by combining the final rule result and corresponding
// mix amount for the rule in each corner
vec4 mac = final36 * max(ma30, ma60) + final30 * ma30 + final60 * ma60
+ final45 * ma45 + finalrn * marn;
/*
Calculate the resulting color by traversing clockwise and counter-clockwise around
the corners of the texel
Finally choose the result that has the largest difference from the texel's original
color
*/
vec3 res1 = P12;
res1 = mix(res1, mix(P13, P17, px.x), mac.x);
res1 = mix(res1, mix(P7, P13, px.y), mac.y);
res1 = mix(res1, mix(P11, P7, px.z), mac.z);
res1 = mix(res1, mix(P17, P11, px.w), mac.w);
vec3 res2 = P12;
res2 = mix(res2, mix(P17, P11, px.w), mac.w);
res2 = mix(res2, mix(P11, P7, px.z), mac.z);
res2 = mix(res2, mix(P7, P13, px.y), mac.y);
res2 = mix(res2, mix(P13, P17, px.x), mac.x);
gl_FragColor = vec4(mix(res1, res2, step(c_df(P12, res1), c_df(P12, res2))),
1.0);
}
着色器接收 2D 纹理，旨在在高分辨率 2D 表面（设备屏幕）上漂亮地缩放它。它是对 SABR 缩放算法的优化，以防万一。
它已经可以工作，并且在非常高端的设备（如 LG Nexus 4）上运行良好，但在较弱的设备上运行速度确实很慢。
对我来说真正重要的设备是带有 Mali 400MP GPU 的三星 Galaxy S 2 \ 3 - 使用此着色器的性能非常糟糕。
到目前为止，我已经尝试过：
- 消除变化（来自 ARM 的 Mali 指南的建议）- 做了微小的改进。
- 用我自己的覆盖 mix() 函数 - 没有好处。
- 将浮点精度降低到 lowp - 没有改变任何东西。
我通过计算渲染时间（eglSwapBuffers 之前和之后）来测量性能——这给了我一个非常线性和一致的性能测量。
除此之外，我真的不知道在哪里看或可以在这里优化什么......
我知道这是一个繁重的算法，我并不是在寻求关于使用哪些替代缩放方法的建议——我已经尝试了很多，这个算法给出了最好的视觉结果。我希望以优化的方式使用完全相同的算法。
更新
我发现如果我使用常量向量而不是依赖向量进行所有纹理提取，我会获得重大的性能提升，所以这显然是一个很大的瓶颈 - 可能是因为缓存。但是，我仍然需要进行这些提取。我玩了至少一些使用 vec2 变化的提取（没有任何混合），但它并没有改善任何东西。我想知道什么可能是有效轮询 21 个纹素的好方法。
我发现计算的主要部分是使用完全相同的一组纹素进行多次 - 因为输出至少按 x2 缩放，并且我使用 GL_NEAREST 进行轮询。至少有 4 个片段落在完全相同的纹素上。如果在高分辨率设备上缩放为 x4，则有 16 个片段落在相同的纹素上——这是一种很大的浪费。有没有办法执行额外的着色器通道来计算在多个片段之间不会改变的所有值？我考虑过渲染到额外的屏幕外纹理，但我需要为每个纹素存储多个值，而不仅仅是一个。
更新
- 尝试使用已知的布尔规则来简化布尔表达式 - 为我节省了一些操作，但对性能没有任何影响。
更新
- 考虑了一种将计算传递给顶点着色器的方法——只有一个“几何”可以创建我的全屏，但是在缩放之前有很多顶点对应于每个原始像素。例如，如果我的原始纹理是 320x200，而我的目标屏幕是 1280x800，则将有 320x200 个顶点均匀分布。然后，在这些顶点中进行大部分计算。问题是 - 我的目标设备（S2 \ S3）不支持顶点纹理采样。
更新
- 在 LG Nexus 4 与三星 Galaxy S3 上测量的性能表明，Nexus 4 的运行速度要快 10 倍以上。怎么会这样？这些是同一代、相同分辨率等的 2 台设备...... Mali 400MP 在某些情况下真的很糟糕吗？我敢肯定，与 Nexus 4 相比，有一些非常具体的东西使它运行得如此缓慢（但还没有找到）。