X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=fft_pass_effect.cpp;h=48e2677576735c5577f3989705cee61a55f4adc4;hp=695a763f0b14f79cd119e527737ff8c4a382e7bc;hb=refs%2Ftags%2F1.1.1;hpb=7f1c8bb8b3ce08b94054f0a8990e5b8225d36036 diff --git a/fft_pass_effect.cpp b/fft_pass_effect.cpp index 695a763..48e2677 100644 --- a/fft_pass_effect.cpp +++ b/fft_pass_effect.cpp @@ -1,7 +1,9 @@ #include #include +#include "effect_chain.h" #include "effect_util.h" +#include "fp16.h" #include "fft_pass_effect.h" #include "util.h" @@ -12,7 +14,12 @@ namespace movit { FFTPassEffect::FFTPassEffect() : input_width(1280), input_height(720), - direction(HORIZONTAL) + direction(HORIZONTAL), + last_fft_size(-1), + last_direction(INVALID), + last_pass_number(-1), + last_inverse(-1), + last_input_size(-1) { register_int("fft_size", &fft_size); register_int("direction", (int *)&direction); @@ -37,22 +44,55 @@ void FFTPassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, { Effect::set_gl_state(glsl_program_num, prefix, sampler_num); - int input_size = (direction == VERTICAL) ? input_height : input_width; + // This is needed because it counteracts the precision issues we get + // because we sample the input texture with normalized coordinates + // (especially when the repeat count along the axis is not a power of + // two); we very rapidly end up in narrowly missing a texel center, + // which causes precision loss to propagate throughout the FFT. + Node *self = chain->find_node_for_effect(this); + glActiveTexture(chain->get_input_sampler(self, 0)); + check_error(); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); + check_error(); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); + check_error(); - // See the comments on changes_output_size() in the .h file to see - // why this is legal. It is _needed_ because it counteracts the - // precision issues we get because we sample the input texture with - // normalized coordinates (especially when the repeat count along - // the axis is not a power of two); we very rapidly end up in narrowly - // missing a texel center, which causes precision loss to propagate - // throughout the FFT. - assert(*sampler_num == 1); - glActiveTexture(GL_TEXTURE0); + // Because of the memory layout (see below) and because we use offsets, + // the support texture values for many consecutive values will be + // the same. Thus, we can store a smaller texture (giving a small + // performance boost) and just sample it with NEAREST. Also, this + // counteracts any precision issues we might get from linear + // interpolation. + glActiveTexture(GL_TEXTURE0 + *sampler_num); + check_error(); + glBindTexture(GL_TEXTURE_2D, tex); check_error(); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); check_error(); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); check_error(); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); + check_error(); + + int input_size = (direction == VERTICAL) ? input_height : input_width; + if (last_fft_size != fft_size || + last_direction != direction || + last_pass_number != pass_number || + last_inverse != inverse || + last_input_size != input_size) { + generate_support_texture(); + } + + set_uniform_int(glsl_program_num, prefix, "support_tex", *sampler_num); + ++*sampler_num; + + assert(input_size % fft_size == 0); + set_uniform_float(glsl_program_num, prefix, "num_repeats", input_size / fft_size); +} + +void FFTPassEffect::generate_support_texture() +{ + int input_size = (direction == VERTICAL) ? input_height : input_width; // The memory layout follows figure 5.2 on page 25 of // http://gpuwave.sesse.net/gpuwave.pdf -- it can be a bit confusing @@ -79,8 +119,8 @@ void FFTPassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, // bit, so the stride is 8, and so on. assert((fft_size & (fft_size - 1)) == 0); // Must be power of two. - float *tmp = new float[fft_size * 4]; int subfft_size = 1 << pass_number; + fp16_int_t *tmp = new fp16_int_t[subfft_size * 4]; double mulfac; if (inverse) { mulfac = 2.0 * M_PI; @@ -91,9 +131,8 @@ void FFTPassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, assert((fft_size & (fft_size - 1)) == 0); // Must be power of two. assert(fft_size % subfft_size == 0); int stride = fft_size / subfft_size; - for (int i = 0; i < fft_size; ++i) { - int k = i / stride; // Element number within this sub-FFT. - int offset = i % stride; // Sub-FFT number. + for (int i = 0; i < subfft_size; i++) { + int k = i; double twiddle_real, twiddle_imag; if (k < subfft_size / 2) { @@ -116,47 +155,41 @@ void FFTPassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, // for using offsets and not direct coordinates as in GPUwave // is that we can have multiple FFTs along the same line, // and want to reuse the support texture by repeating it. - int base = k * stride * 2 + offset; - int support_texture_index; + int base = k * stride * 2; + int support_texture_index = i; + int src1 = base; + int src2 = base + stride; + double sign = 1.0; if (direction == FFTPassEffect::VERTICAL) { // Compensate for OpenGL's bottom-left convention. - support_texture_index = fft_size - i - 1; - } else { - support_texture_index = i; + support_texture_index = subfft_size - support_texture_index - 1; + sign = -1.0; } - tmp[support_texture_index * 4 + 0] = (base - support_texture_index) / double(input_size); - tmp[support_texture_index * 4 + 1] = (base + stride - support_texture_index) / double(input_size); - tmp[support_texture_index * 4 + 2] = twiddle_real; - tmp[support_texture_index * 4 + 3] = twiddle_imag; + tmp[support_texture_index * 4 + 0] = fp64_to_fp16(sign * (src1 - i * stride) / double(input_size)); + tmp[support_texture_index * 4 + 1] = fp64_to_fp16(sign * (src2 - i * stride) / double(input_size)); + tmp[support_texture_index * 4 + 2] = fp64_to_fp16(twiddle_real); + tmp[support_texture_index * 4 + 3] = fp64_to_fp16(twiddle_imag); } - glActiveTexture(GL_TEXTURE0 + *sampler_num); - check_error(); - glBindTexture(GL_TEXTURE_2D, tex); - check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); - check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); - check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); - check_error(); - // Supposedly FFTs are very sensitive to inaccuracies in the twiddle factors, // at least according to a paper by Schatzman (see gpuwave.pdf reference [30] - // for the full reference), so we keep them at 32-bit. However, for - // small sizes, all components are exact anyway, so we can cheat there - // (although noting that the source coordinates become somewhat less - // accurate then, too). - glTexImage2D(GL_TEXTURE_2D, 0, (subfft_size <= 4) ? GL_RGBA16F : GL_RGBA32F, fft_size, 1, 0, GL_RGBA, GL_FLOAT, tmp); + // for the full reference); however, practical testing indicates that it's + // not a problem to keep the twiddle factors at 16-bit, at least as long as + // we round them properly--it would seem that Schatzman were mainly talking + // about poor sin()/cos() approximations. Thus, we store them in 16-bit, + // which gives a nice speed boost. + // + // Note that the source coordinates become somewhat less accurate too, though. + glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, subfft_size, 1, 0, GL_RGBA, GL_HALF_FLOAT, tmp); check_error(); delete[] tmp; - set_uniform_int(glsl_program_num, prefix, "support_tex", *sampler_num); - ++*sampler_num; - - assert(input_size % fft_size == 0); - set_uniform_float(glsl_program_num, prefix, "num_repeats", input_size / fft_size); + last_fft_size = fft_size; + last_direction = direction; + last_pass_number = pass_number; + last_inverse = inverse; + last_input_size = input_size; } } // namespace movit