99 lines
3.3 KiB
Metal
99 lines
3.3 KiB
Metal
//
|
|
// TerrainAlgorithms.metal
|
|
// Terrain2
|
|
//
|
|
// Created by Eryn Wells on 11/4/18.
|
|
// Copyright © 2018 Eryn Wells. All rights reserved.
|
|
//
|
|
|
|
#include <metal_stdlib>
|
|
#include <metal_types>
|
|
#include "ShaderTypes.h"
|
|
using namespace metal;
|
|
|
|
/// A pseudo-random number generator providing several algorithms.
|
|
/// - http://reedbeta.com/blog/quick-and-easy-gpu-random-numbers-in-d3d11/
|
|
struct PRNG {
|
|
PRNG(uint seed) : mSeed(wangHash(seed)) { }
|
|
|
|
/// Generate a random unsigned integer using a linear congruential generator.
|
|
uint lcg() {
|
|
mSeed = 1664525 * mSeed + 1013904223;
|
|
return mSeed;
|
|
}
|
|
|
|
/// Generate a random unsigned integer using the Xorshift algorithm from George Marsaglia's paper.
|
|
uint xorShift() {
|
|
mSeed ^= (mSeed << 13);
|
|
mSeed ^= (mSeed >> 17);
|
|
mSeed ^= (mSeed << 5);
|
|
return mSeed;
|
|
}
|
|
|
|
uint wangHash(uint seed) {
|
|
seed = (seed ^ 61) ^ (seed >> 16);
|
|
seed *= 9;
|
|
seed = seed ^ (seed >> 4);
|
|
seed *= 0x27d4eb2d;
|
|
seed = seed ^ (seed >> 15);
|
|
return seed;
|
|
}
|
|
|
|
private:
|
|
uint mSeed;
|
|
};
|
|
|
|
kernel void updateGeometryHeights(texture2d<float> texture [[texture(GeneratorTextureIndexIn)]],
|
|
constant float2 *texCoords [[buffer(GeneratorBufferIndexTexCoords)]],
|
|
constant Uniforms &uniforms [[buffer(GeneratorBufferIndexUniforms)]],
|
|
device packed_float3 *vertexes [[buffer(GeneratorBufferIndexMeshPositions)]],
|
|
uint2 tid [[thread_position_in_grid]])
|
|
{
|
|
constexpr sampler s(coord::normalized, address::clamp_to_zero, filter::linear);
|
|
|
|
const uint vIdx = tid.y * uniforms.terrainSegments.x + tid.x;
|
|
|
|
// Get the height from the texture.
|
|
float2 texCoord = texCoords[vIdx];
|
|
float4 height = texture.sample(s, texCoord);
|
|
|
|
// Update the vertex data.
|
|
vertexes[vIdx].y = height.r;
|
|
}
|
|
|
|
kernel void updateGeometryNormals(constant float3 *vertexes [[buffer(GeneratorBufferIndexMeshPositions)]],
|
|
constant packed_uint3 *indexes [[buffer(GeneratorBufferIndexIndexes)]],
|
|
device packed_float3 *normals [[buffer(GeneratorBufferIndexFaceNormals)]],
|
|
uint tid [[thread_position_in_grid]])
|
|
{
|
|
const uint3 triIdx = indexes[tid];
|
|
float3 side1(vertexes[triIdx.y] - vertexes[triIdx.x]);
|
|
float3 side2(vertexes[triIdx.y] - vertexes[triIdx.z]);
|
|
float3 normal(normalize(cross(side1, side2)));
|
|
normals[tid] = normal;
|
|
}
|
|
|
|
kernel void updateGeometryVertexNormals()
|
|
{
|
|
|
|
}
|
|
|
|
#pragma mark - ZeroGenerator
|
|
|
|
kernel void zeroKernel(texture2d<float, access::write> outTexture [[texture(GeneratorTextureIndexOut)]],
|
|
uint2 tid [[thread_position_in_grid]])
|
|
{
|
|
outTexture.write(0, tid);
|
|
}
|
|
|
|
#pragma mark - RandomGenerator
|
|
|
|
kernel void randomKernel(texture2d<float, access::write> outTexture [[texture(GeneratorTextureIndexOut)]],
|
|
constant RandomAlgorithmUniforms &uniforms [[buffer(0)]],
|
|
uint2 tid [[thread_position_in_grid]])
|
|
{
|
|
PRNG rng(uniforms.randoms[(tid.x * tid.y) % kRandomAlgorithmUniforms_RandomCount]);
|
|
uint r = rng.xorShift();
|
|
float x = float(r * (1.0 / float(UINT_MAX))) * 0.5f;
|
|
outTexture.write(x, tid);
|
|
}
|