Test a blit shader implementation

assets/blit.slang

@@ -0,0 +1,37 @@
+// Prism fullscreen texture blit shader.
+//
+// Draws a selected texture from the bindless array as a fullscreen quad that
+// is letterboxed/pillarboxed to preserve aspect ratio (contain-fit). The NDC
+// content rect is supplied via push constants so the texture is never
+// stretched, squashed, or cropped.
+
+struct BlitData {
+	float4 rect;   // NDC fit rect: x0, y0, x1, y1
+	uint   selected;
+	uint   pad[3];
+};
+
+[[vk::push_constant]]
+BlitData blit;
+
+Sampler2D textures[];
+
+struct VSOutput {
+	float4 Pos : SV_POSITION;
+	float2 UV;
+};
+
+[shader("vertex")]
+VSOutput main(uint vertexIndex : SV_VertexID) {
+	VSOutput output;
+	float2 uv = float2(float(vertexIndex & 1), float((vertexIndex >> 1) & 1));
+	output.UV = uv;
+	float2 pos = lerp(blit.rect.xy, blit.rect.zw, uv);
+	output.Pos = float4(pos, 0.0, 1.0);
+	return output;
+}
+
+[shader("fragment")]
+float4 main(VSOutput input) {
+	return textures[NonUniformResourceIndex(blit.selected)].Sample(input.UV);
+}

assets/shader.slang

@@ -1,61 +0,0 @@
-/* Copyright (c) 2025-2026, Sascha Willems
- *
- * SPDX-License-Identifier: MIT
- *
- */
-
-struct VSInput {
-	float3 Pos;
-	float3 Normal;
-	float2 UV;
-};
-
-Sampler2D textures[];
-
-struct ShaderData {
-	float4x4 projection;
-	float4x4 view;
-	float4x4 model[3];
-	float4 lightPos;
-	uint32_t selected;
-};
-
-struct VSOutput {
-	float4 Pos : SV_POSITION;
-	float3 Normal;
-	float2 UV;
-	float3 Factor;
-	float3 LightVec;
-	float3 ViewVec;
-	uint32_t InstanceIndex;
-};
-
-[shader("vertex")]
-VSOutput main(VSInput input, uniform ShaderData *shaderData, uint instanceIndex : SV_VulkanInstanceID) {
-	VSOutput output;
-	float4x4 modelMat = shaderData->model[instanceIndex];
-	output.Normal = mul((float3x3)mul(shaderData->view, modelMat), input.Normal);
-	output.UV = input.UV;
-	output.Pos = mul(shaderData->projection, mul(shaderData->view, mul(modelMat, float4(input.Pos.xyz, 1.0))));
-	output.Factor = (shaderData->selected == instanceIndex ? 3.0f : 1.0f);
-	output.InstanceIndex = instanceIndex;
-	// Calculate view vectors required for lighting
-	float4 fragPos = mul(mul(shaderData->view, modelMat), float4(input.Pos.xyz, 1.0));
-	output.LightVec = shaderData->lightPos.xyz - fragPos.xyz;
-	output.ViewVec = -fragPos.xyz;
-	return output;
-}
-
-[shader("fragment")]
-float4 main(VSOutput input) {
-	// Phong lighting
-	float3 N = normalize(input.Normal);
-	float3 L = normalize(input.LightVec);
-	float3 V = normalize(input.ViewVec);
-	float3 R = reflect(-L, N);
-	float3 diffuse = max(dot(N, L), 0.0025);
-	float3 specular = pow(max(dot(R, V), 0.0), 16.0) * 0.75;
-	// Sample from texture
-	float3 color = textures[NonUniformResourceIndex(input.InstanceIndex)].Sample(input.UV).rgb * input.Factor;
-	return float4(diffuse * color.rgb + specular, 1.0);
-}

assets/suzanne.mtl

@@ -1,62 +0,0 @@
-# Blender 5.0.1 MTL File: 'suzanne4.blend'
-# www.blender.org
-
-newmtl Material
-Ns 250.000000
-Ka 1.000000 1.000000 1.000000
-Kd 0.800000 0.800000 0.800000
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.500000
-d 1.000000
-illum 2
-
-newmtl Material.001
-Ns 250.000000
-Ka 1.000000 1.000000 1.000000
-Kd 0.127605 0.127605 0.127605
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.500000
-d 1.000000
-illum 2
-
-newmtl Material.002
-Ns 250.000000
-Ka 1.000000 1.000000 1.000000
-Kd 0.000000 0.000000 0.000000
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.500000
-d 1.000000
-illum 2
-
-newmtl Material.003
-Ns 250.000000
-Ka 1.000000 1.000000 1.000000
-Kd 0.800000 0.800000 0.800000
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.500000
-d 1.000000
-illum 2
-
-newmtl Material.004
-Ns 250.000000
-Ka 1.000000 1.000000 1.000000
-Kd 0.800007 0.200800 0.327761
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.500000
-d 1.000000
-illum 2
-
-newmtl Material.005
-Ns 250.000000
-Ka 1.000000 1.000000 1.000000
-Kd 1.000000 1.000000 1.000000
-Ks 0.500000 0.500000 0.500000
-Ke 0.000000 0.000000 0.000000
-Ni 1.500000
-d 1.000000
-illum 2