Allow for more than ten bits in subpixel precision measuring; modern llvmpipe seems...

[movit] / resample_effect.cpp

diff --git a/resample_effect.cpp b/resample_effect.cpp
index e1e6199ec5b5b857add0df623d6fd05a25d4b1e0..ec4f67edad5d628dcf0b9ab555d50cb4b747b957 100644 (file)
--- a/resample_effect.cpp
+++ b/resample_effect.cpp
@@ -3,11 +3,11 @@
 
 #include <math.h>
 #include <assert.h>
+#include <GL/glew.h>
 
 #include "resample_effect.h"
 #include "effect_chain.h"
 #include "util.h"
-#include "opengl.h"
 
 namespace {
 
@@ -74,9 +74,12 @@ unsigned combine_samples(float *src, float *dst, unsigned num_src_samples, unsig
                float offset, total_weight, sum_sq_error;
                combine_two_samples(w1, w2, &offset, &total_weight, &sum_sq_error);
 
-               // If the interpolation error is larger than that of one level
-               // at 8-bit precision, don't combine.
-               if (sum_sq_error > 1.0f / (256.0f * 256.0f)) {
+               // If the interpolation error is larger than that of about sqrt(2) of
+               // a level at 8-bit precision, don't combine. (You'd think 1.0 was enough,
+               // but since the artifacts are not really random, they can get quite
+               // visible. On the other hand, going to 0.25f, I can see no change at
+               // all with 8-bit output, so it would not seem to be worth it.)
+               if (sum_sq_error > 0.5f / (256.0f * 256.0f)) {
                        continue;
                }
 
@@ -345,6 +348,11 @@ void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std::
 {
        Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
 
+       assert(input_width > 0);
+       assert(input_height > 0);
+       assert(output_width > 0);
+       assert(output_height > 0);
+
        if (input_width != last_input_width ||
            input_height != last_input_height ||
            output_width != last_output_width ||