metal: fix gpu hang during envmap filtering

paint/shaders/prefilter_envmap.kong

@@ -1,7 +1,7 @@
 
 #[set(everything)]
 const constants: {
-	params: float4; // level, constants.params.y
+	params: float4; // level, samples, alpha, pass
 };
 
 #[set(everything)]
@@ -65,13 +65,13 @@ fun cos_weighted_hemisphere_direction(n: float3, co: float2, seed: float): float
 }
 
 fun prefilter_envmap_frag(input: vert_out): float4 {
-	var color: float4 = float4(0.0, 0.0, 0.0, 1.0);
+	var color: float4 = float4(0.0, 0.0, 0.0, constants.params.z);
 	var n: float3 = reverse_equirect(input.tex);
 
 	//for (var i: int = 0; i < int(constants.params.y); i += 1) {
 	var i: int = 0;
 	while (i < int(constants.params.y)) {
-		var dir: float3 = normalize(lerp3(n, cos_weighted_hemisphere_direction(n, input.tex, float(i)), constants.params.x));
+		var dir: float3 = normalize(lerp3(n, cos_weighted_hemisphere_direction(n, input.tex, float(i + constants.params.w * constants.params.y)), constants.params.x));
 		var sampled: float3 = sample(radiance, sampler_linear, equirect(dir)).rgb;
 		sampled = min3(sampled, float3(10.0, 10.0, 10.0));
 		color.rgb = color.rgb + sampled;

paint/sources/import_envmap.ts

@@ -14,6 +14,8 @@ function import_envmap_run(path: string, image: gpu_texture_t) {
 		import_envmap_pipeline                   = gpu_create_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_t.SOURCE_ALPHA;
+		import_envmap_pipeline.blend_destination = gpu_blend_t.ONE;
 		let vs: gpu_vertex_structure_t         = {};
 		gpu_vertex_struct_add(vs, "pos", gpu_vertex_data_t.F32_2X);
 		import_envmap_pipeline.input_layout                      = vs;
@@ -68,22 +70,29 @@ function import_envmap_run(path: string, image: gpu_texture_t) {
 }
 
 function import_envmap_get_radiance_mip(mip: gpu_texture_t, level: i32, radiance: gpu_texture_t) {
-	_gpu_begin(mip);
+	/// if arm_metal
+	let pass_count: i32 = 8; // 32;
+	import_envmap_params.y = 512;
+	/// else
+	let pass_count: i32 = 1;
+	import_envmap_params.y = 1024 * 16;
+	/// end
+	import_envmap_params.z = 1.0 / pass_count;
+	import_envmap_params.x = (level + 1) / 10;
+
+	for (let i: i32 = 0; i < pass_count; ++i) {
+		_gpu_begin(mip, null, null, i == 0 ? gpu_clear_t.COLOR : gpu_clear_t.NONE, 0x00000000);
 		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.x = (level + 1) / 10;
-	/// if (arm_macos || arm_ios)
-	import_envmap_params.y = 1024 * 2; // Prevent gpu hang
-	/// else
-	import_envmap_params.y = 1024 * 16;
-	/// end
+		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);
 		let noise: gpu_texture_t = data_get_image("bnoise256.k");
 		gpu_set_texture(import_envmap_noise_loc, noise);
 		gpu_draw();
 		gpu_end();
+	}
 }
 
 function import_envmap_reverse_equirect(x: f32, y: f32): vec4_t {