float *dither_noise = new float[width * height];
float dither_double_amplitude = 1.0f / (1 << num_bits);
+ // We don't need a strictly nonrepeating dither; reducing the resolution
+ // to max 128x128 saves a lot of texture bandwidth, without causing any
+ // noticeable harm to the dither's performance.
+ texture_width = std::min(width, 128);
+ texture_height = std::min(height, 128);
+
// Using the resolution as a seed gives us a consistent dither from frame to frame.
// It also gives a different dither for e.g. different aspect ratios, which _feels_
// good, but probably shouldn't matter.
unsigned seed = (width << 16) ^ height;
- for (int i = 0; i < width * height; ++i) {
+ for (int i = 0; i < texture_width * texture_height; ++i) {
seed = lcg_rand(seed);
float normalized_rand = seed * (1.0f / (1U << 31)) - 0.5; // [-0.5, 0.5>
dither_noise[i] = dither_double_amplitude * normalized_rand;
check_error();
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
check_error();
- glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+ check_error();
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
check_error();
- glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
check_error();
- glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE16F_ARB, width, height, 0, GL_LUMINANCE, GL_FLOAT, dither_noise);
+ glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE16F_ARB, texture_width, texture_height, 0, GL_LUMINANCE, GL_FLOAT, dither_noise);
check_error();
delete[] dither_noise;
set_uniform_int(glsl_program_num, prefix, "dither_tex", *sampler_num);
++sampler_num;
+
+ // In theory, we should adjust for the texel centers that have moved here as well,
+ // but since we use GL_NEAREST and we don't really care a lot what texel we sample,
+ // we don't have to worry about it.
+ float tc_scale[] = { float(width) / float(texture_width), float(height) / float(texture_height) };
+ set_uniform_vec2(glsl_program_num, prefix, "tc_scale", tc_scale);
}