Add shaders re-implemented in HLSL

These were written against the shaders at revision eddd724e7.
There have been changes made since then, which will need to be mirrored.

See `data/hlsl/README.md` for the current status of each sample.

data/hlsl/computenbody/particle.frag

@@ -0,0 +1,21 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureColorMap : register(t0);
+SamplerState samplerColorMap : register(s0);
+Texture2D textureGradientRamp : register(t1);
+SamplerState samplerGradientRamp : register(s1);
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float GradientPos : POSITION0;
+[[vk::location(1)]] float2 CenterPos : POSITION1;
+[[vk::location(2)]] float PointSize : TEXCOORD0;
+};
+
+float4 main (VSOutput input)  : SV_TARGET
+{
+	float3 color = textureGradientRamp.Sample(samplerGradientRamp, float2(input.GradientPos, 0.0)).rgb;
+	float2 PointCoord = (input.Pos.xy - input.CenterPos.xy) / input.PointSize + 0.5;
+	return float4(textureColorMap.Sample(samplerColorMap, PointCoord).rgb * color, 1);
+}

data/hlsl/computenbody/particle.vert

@@ -0,0 +1,41 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+[[vk::location(0)]] float4 Pos : POSITION0;
+[[vk::location(1)]] float4 Vel : TEXCOORD0;
+};
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float GradientPos : POSITION0;
+[[vk::location(1)]] float2 CenterPos : POSITION1;
+[[vk::builtin("PointSize")]] float PSize : PSIZE;
+[[vk::location(2)]] float PointSize : TEXCOORD0;
+};
+
+struct UBO
+{
+	float4x4 projection;
+	float4x4 modelview;
+	float2 screendim;
+};
+
+cbuffer ubo : register(b2) { UBO ubo; }
+
+VSOutput main (VSInput input)
+{
+	VSOutput output = (VSOutput)0;
+	const float spriteSize = 0.005 * input.Pos.w; // Point size influenced by mass (stored in input.Pos.w);
+
+	float4 eyePos = mul(ubo.modelview, float4(input.Pos.x, input.Pos.y, input.Pos.z, 1.0));
+	float4 projectedCorner = mul(ubo.projection, float4(0.5 * spriteSize, 0.5 * spriteSize, eyePos.z, eyePos.w));
+	output.PSize = output.PointSize = clamp(ubo.screendim.x * projectedCorner.x / projectedCorner.w, 1.0, 128.0);
+
+	output.Pos = mul(ubo.projection, eyePos);
+	output.CenterPos = ((output.Pos.xy / output.Pos.w) + 1.0) * 0.5 * ubo.screendim;
+
+	output.GradientPos = input.Vel.w;
+	return output;
+}

data/hlsl/computenbody/particle_calculate.comp

@@ -0,0 +1,70 @@
+// Copyright 2020 Google LLC
+
+struct Particle
+{
+	float4 pos;
+	float4 vel;
+};
+
+// Binding 0 : Position storage buffer
+RWStructuredBuffer<Particle> particles : register(u0);
+
+struct UBO
+{
+	float deltaT;
+	int particleCount;
+};
+
+cbuffer ubo : register(b1) { UBO ubo; }
+
+#define MAX_SHARED_DATA_SIZE 1024
+[[vk::constant_id(0)]] const int SHARED_DATA_SIZE = 512;
+[[vk::constant_id(1)]] const float GRAVITY = 0.002;
+[[vk::constant_id(2)]] const float POWER = 0.75;
+[[vk::constant_id(3)]] const float SOFTEN = 0.0075;
+
+// Share data between computer shader invocations to speed up caluclations
+groupshared float4 sharedData[MAX_SHARED_DATA_SIZE];
+
+[numthreads(256, 1, 1)]
+void main(uint3 GlobalInvocationID : SV_DispatchThreadID, uint3 LocalInvocationID : SV_GroupThreadID)
+{
+	// Current SSBO index
+	uint index = GlobalInvocationID.x;
+	if (index >= ubo.particleCount)
+		return;
+
+	float4 position = particles[index].pos;
+	float4 velocity = particles[index].vel;
+	float4 acceleration = float4(0, 0, 0, 0);
+
+	for (int i = 0; i < ubo.particleCount; i += SHARED_DATA_SIZE)
+	{
+		if (i + LocalInvocationID.x < ubo.particleCount)
+		{
+			sharedData[LocalInvocationID.x] = particles[i + LocalInvocationID.x].pos;
+		}
+		else
+		{
+			sharedData[LocalInvocationID.x] = float4(0, 0, 0, 0);
+		}
+
+		GroupMemoryBarrierWithGroupSync();
+
+		for (int j = 0; j < 256; j++)
+		{
+			float4 other = sharedData[j];
+			float3 len = other.xyz - position.xyz;
+			acceleration.xyz += GRAVITY * len * other.w / pow(dot(len, len) + SOFTEN, POWER);
+		}
+
+		GroupMemoryBarrierWithGroupSync();
+	}
+
+	particles[index].vel.xyz += ubo.deltaT * acceleration.xyz;
+
+	// Gradient texture position
+	particles[index].vel.w += 0.1 * ubo.deltaT;
+	if (particles[index].vel.w > 1.0)
+		particles[index].vel.w -= 1.0;
+}

data/hlsl/computenbody/particle_integrate.comp

@@ -0,0 +1,28 @@
+// Copyright 2020 Google LLC
+
+struct Particle
+{
+	float4 pos;
+	float4 vel;
+};
+
+// Binding 0 : Position storage buffer
+RWStructuredBuffer<Particle> particles : register(u0);
+
+struct UBO
+{
+	float deltaT;
+	int particleCount;
+};
+
+cbuffer ubo : register(b1) { UBO ubo; }
+
+[numthreads(256, 1, 1)]
+void main(uint3 GlobalInvocationID : SV_DispatchThreadID)
+{
+	int index = int(GlobalInvocationID.x);
+	float4 position = particles[index].pos;
+	float4 velocity = particles[index].vel;
+	position += ubo.deltaT * velocity;
+	particles[index].pos = position;
+}