armorpaint/paint/sources/import_envmap.c

#include "global.h"

void import_envmap_run(char *path, gpu_texture_t *image) {
	// Init
	if (import_envmap_pipeline == NULL) {
		gc_unroot(import_envmap_pipeline);
		import_envmap_pipeline = gpu_create_pipeline();
		gc_root(import_envmap_pipeline);
		import_envmap_pipeline->vertex_shader     = sys_get_shader("prefilter_envmap.vert");
		import_envmap_pipeline->fragment_shader   = sys_get_shader("prefilter_envmap.frag");
		import_envmap_pipeline->blend_source      = GPU_BLEND_SOURCE_ALPHA;
		import_envmap_pipeline->blend_destination = GPU_BLEND_ONE;
		gpu_vertex_structure_t *vs                = GC_ALLOC_INIT(gpu_vertex_structure_t, {0});
		gpu_vertex_struct_add(vs, "pos", GPU_VERTEX_DATA_F32_2X);
		import_envmap_pipeline->input_layout                      = vs;
		import_envmap_pipeline->color_attachment_count            = 1;
		import_envmap_pipeline->color_attachment[0] = GPU_TEXTURE_FORMAT_RGBA64;

		gpu_pipeline_compile(import_envmap_pipeline);
		import_envmap_params_loc   = 0;
		import_envmap_radiance_loc = 0;
		import_envmap_noise_loc    = 1;

		gc_unroot(import_envmap_radiance);
		import_envmap_radiance = gpu_create_render_target(1024, 512, GPU_TEXTURE_FORMAT_RGBA64);
		gc_root(import_envmap_radiance);

		gc_unroot(import_envmap_mips);
		import_envmap_mips = any_array_create_from_raw((void *[]){}, 0);
		gc_root(import_envmap_mips);
		i32 w = 512;
		for (i32 i = 0; i < 5; ++i) {
			any_array_push(import_envmap_mips, gpu_create_render_target(w, w > 1 ? math_floor(w / (float)2) : 1, GPU_TEXTURE_FORMAT_RGBA64));
			w = math_floor(w / (float)2);
		}
	}

	// Down-scale to 1024x512
	draw_begin(import_envmap_radiance, false, 0);
	draw_set_pipeline(pipes_copy64);
	draw_scaled_image(image, 0, 0, 1024, 512);
	draw_set_pipeline(NULL);
	draw_end();

	// Radiance
	for (i32 i = 0; i < import_envmap_mips->length; ++i) {
		import_envmap_get_radiance_mip(import_envmap_mips->buffer[i], i, import_envmap_radiance);
	}

	// Irradiance
	buffer_t *radiance_pixels        = gpu_get_texture_pixels(import_envmap_radiance);
	scene_world->_->irradiance       = import_envmap_get_spherical_harmonics(radiance_pixels, import_envmap_radiance->width, import_envmap_radiance->height);

	// World
	scene_world->strength            = 1.0;
	scene_world->radiance_mipmaps    = import_envmap_mips->length - 2;
	scene_world->_->envmap           = image;
	scene_world->envmap              = string_copy(path);
	scene_world->_->radiance         = import_envmap_radiance;
	scene_world->_->radiance_mipmaps = import_envmap_mips;
	context_raw->saved_envmap        = image;
	context_raw->show_envmap         = true;
	if (context_raw->show_envmap_blur) {
		scene_world->_->envmap = scene_world->_->radiance_mipmaps->buffer[0];
	}
	context_raw->ddirty = 2;
	project_raw->envmap = string_copy(path);
}

void import_envmap_get_radiance_mip(gpu_texture_t *mip, i32 level, gpu_texture_t *radiance) {
	#ifdef IRON_METAL
	i32 pass_count         = 8; // 32;
	import_envmap_params.y = 512;
	#else
	i32 pass_count         = 1;
	import_envmap_params.y = 1024 * 16;
	#endif
	import_envmap_params.z = 1.0 / (float)pass_count;
	import_envmap_params.x = (level + 1) / (float)10;

	for (i32 i = 0; i < pass_count; ++i) {
		_gpu_begin(mip, NULL, NULL, i == 0 ? GPU_CLEAR_COLOR : GPU_CLEAR_NONE, 0x00000000, 0.0);
		gpu_set_vertex_buffer(const_data_screen_aligned_vb);
		gpu_set_index_buffer(const_data_screen_aligned_ib);
		gpu_set_pipeline(import_envmap_pipeline);
		import_envmap_params.w = i;
		gpu_set_float4(import_envmap_params_loc, import_envmap_params.x, import_envmap_params.y, import_envmap_params.z, import_envmap_params.w);
		gpu_set_texture(import_envmap_radiance_loc, radiance);
		gpu_texture_t *noise = data_get_image("bnoise256.k");
		gpu_set_texture(import_envmap_noise_loc, noise);
		gpu_draw();
		gpu_end();
	}
}

vec4_t import_envmap_reverse_equirect(f32 x, f32 y) {
	f32 theta       = x * math_pi() * 2 - math_pi();
	f32 phi         = y * math_pi();
	// return n.set(math_sin(phi) * math_cos(theta), -(math_sin(phi) * math_sin(theta)), math_cos(phi));
	import_envmap_n = vec4_create(-math_cos(phi), math_sin(phi) * math_cos(theta), -(math_sin(phi) * math_sin(theta)), 1.0);
	return import_envmap_n;
}

// https://ndotl.wordpress.com/2015/03/07/pbr-cubemap-filtering
// https://seblagarde.wordpress.com/2012/06/10/amd-cubemapgen-for-physically-based-rendering
f32_array_t *import_envmap_get_spherical_harmonics(buffer_t *source, i32 source_width, i32 source_height) {
	f32_array_t *sh      = f32_array_create(9 * 3 + 1); // Align to mult of 4 - 27->28
	f32          accum   = 0.0;
	f32          weight  = 1.0;
	f32          weight1 = weight * 4 / (float)17;
	f32          weight2 = weight * 8 / (float)17;
	f32          weight3 = weight * 15 / (float)17;
	f32          weight4 = weight * 5 / (float)68;
	f32          weight5 = weight * 15 / (float)68;

	for (i32 x = 0; x < source_width; ++x) {
		for (i32 y = 0; y < source_height; ++y) {
			import_envmap_n = import_envmap_reverse_equirect(x / (float)source_width, y / (float)source_height);

			for (i32 i = 0; i < 3; ++i) {
				f32 value = buffer_get_f16(source, ((x + y * source_width) * 8 + i * 2));
				value     = math_pow(value, 1.0 / (float)2.2);

				sh->buffer[0 + i] += value * weight1;
				sh->buffer[3 + i] += value * weight2 * import_envmap_n.x;
				sh->buffer[6 + i] += value * weight2 * import_envmap_n.y;
				sh->buffer[9 + i] += value * weight2 * import_envmap_n.z;

				sh->buffer[12 + i] += value * weight3 * import_envmap_n.x * import_envmap_n.z;
				sh->buffer[15 + i] += value * weight3 * import_envmap_n.z * import_envmap_n.y;
				sh->buffer[18 + i] += value * weight3 * import_envmap_n.y * import_envmap_n.x;

				sh->buffer[21 + i] += value * weight4 * (3.0 * import_envmap_n.z * import_envmap_n.z - 1.0);
				sh->buffer[24 + i] += value * weight5 * (import_envmap_n.x * import_envmap_n.x - import_envmap_n.y * import_envmap_n.y);

				accum += weight;
			}
		}
	}

	for (i32 i = 0; i < sh->length; ++i) {
		sh->buffer[i] /= accum / (float)16;
	}

	return sh;
}