X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=dither_effect.cpp;h=1554356213ee1ec13815fd0c5581140010d15d74;hp=cdfb157e675900a08ed3a859889641e01df7ba4a;hb=d4f00f9f47a0efaefabaf1efa1a0e214eeecca67;hpb=ff9e68a3f5abb179bd7bf9fb84df48327f148583

diff --git a/dither_effect.cpp b/dither_effect.cpp
index cdfb157..1554356 100644
--- a/dither_effect.cpp
+++ b/dither_effect.cpp
@@ -1,9 +1,10 @@
-#include <math.h>
+#include <GL/glew.h>
 #include <assert.h>
+#include <algorithm>
 
 #include "dither_effect.h"
+#include "effect_util.h"
 #include "util.h"
-#include "opengl.h"
 
 namespace {
 
@@ -47,11 +48,17 @@ void DitherEffect::update_texture(GLuint glsl_program_num, const std::string &pr
 	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;
@@ -63,11 +70,13 @@ void DitherEffect::update_texture(GLuint glsl_program_num, const std::string &pr
 	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;
@@ -77,6 +86,10 @@ void DitherEffect::set_gl_state(GLuint glsl_program_num, const std::string &pref
 {
 	Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
 
+	assert(width > 0);
+	assert(height > 0);
+	assert(num_bits > 0);
+
 	if (width != last_width || height != last_height || num_bits != last_num_bits) {
 		update_texture(glsl_program_num, prefix, sampler_num);
 		last_width = width;
@@ -91,4 +104,10 @@ void DitherEffect::set_gl_state(GLuint glsl_program_num, const std::string &pref
 
 	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);
 }