cuda-samples/Samples/lineOfSight/lineOfSight.cu

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/* Copyright (c) 2021, NVIDIA CORPORATION. All rights reserved.
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// This sample is an implementation of a simple line-of-sight algorithm:
// Given a height map and a ray originating at some observation point,
// it computes all the points along the ray that are visible from the
// observation point.
// It is based on the description made in "Guy E. Blelloch. Vector models
// for data-parallel computing. MIT Press, 1990" and uses open source CUDA
// Thrust Library
#ifdef _WIN32
#define NOMINMAX
#endif
// includes, system
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <float.h>
// includes, project
#include <helper_functions.h>
#include <helper_cuda.h>
#include <helper_math.h>
// includes, library
#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/scan.h>
#include <thrust/copy.h>
////////////////////////////////////////////////////////////////////////////////
// declaration, types
// Boolean
typedef unsigned char Bool;
enum { False = 0, True = 1 };
// 2D height field
struct HeightField {
int width;
float *height;
};
// Ray
struct Ray {
float3 origin;
float2 dir;
int length;
float oneOverLength;
};
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
// declaration, forward
int runTest(int argc, char **argv);
__global__ void computeAngles_kernel(const Ray, float *, cudaTextureObject_t);
__global__ void computeVisibilities_kernel(const float *, const float *, int,
Bool *);
void lineOfSight_gold(const HeightField, const Ray, Bool *);
__device__ __host__ float2 getLocation(const Ray, int);
__device__ __host__ float getAngle(const Ray, float2, float);
////////////////////////////////////////////////////////////////////////////////
// Program main
////////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv) {
int res = runTest(argc, argv);
if (res != 1) {
printf("Test failed!\n");
exit(EXIT_FAILURE);
}
printf("Test passed\n");
exit(EXIT_SUCCESS);
}
////////////////////////////////////////////////////////////////////////////////
//! Run a line-of-sight test for CUDA
////////////////////////////////////////////////////////////////////////////////
int runTest(int argc, char **argv) {
////////////////////////////////////////////////////////////////////////////
// Device initialization
printf("[%s] - Starting...\n", argv[0]);
// use command-line specified CUDA device, otherwise use device with highest
// Gflops/s
findCudaDevice(argc, (const char **)argv);
////////////////////////////////////////////////////////////////////////////
// Timer
// Create
StopWatchInterface *timer;
sdkCreateTimer(&timer);
// Number of iterations to get accurate timing
uint numIterations = 100;
////////////////////////////////////////////////////////////////////////////
// Height field
HeightField heightField;
// Allocate in host memory
int2 dim = make_int2(10000, 100);
heightField.width = dim.x;
thrust::host_vector<float> height(dim.x * dim.y);
heightField.height = (float *)&height[0];
//
// Fill in with an arbitrary sine surface
for (int x = 0; x < dim.x; ++x)
for (int y = 0; y < dim.y; ++y) {
float amp = 0.1f * (x + y);
float period = 2.0f + amp;
*(heightField.height + dim.x * y + x) =
amp * (sinf(sqrtf((float)(x * x + y * y)) * 2.0f * 3.1416f / period) +
1.0f);
}
// Allocate CUDA array in device memory
cudaChannelFormatDesc channelDesc =
cudaCreateChannelDesc(32, 0, 0, 0, cudaChannelFormatKindFloat);
cudaArray *heightFieldArray;
checkCudaErrors(
cudaMallocArray(&heightFieldArray, &channelDesc, dim.x, dim.y));
// Initialize device memory
checkCudaErrors(cudaMemcpy2DToArray(
heightFieldArray, 0, 0, heightField.height, dim.x * sizeof(float),
dim.x * sizeof(float), dim.y, cudaMemcpyHostToDevice));
cudaTextureObject_t heightFieldTex;
cudaResourceDesc texRes;
memset(&texRes, 0, sizeof(cudaResourceDesc));
texRes.resType = cudaResourceTypeArray;
texRes.res.array.array = heightFieldArray;
cudaTextureDesc texDescr;
memset(&texDescr, 0, sizeof(cudaTextureDesc));
texDescr.normalizedCoords = false;
texDescr.filterMode = cudaFilterModePoint;
texDescr.addressMode[0] = cudaAddressModeClamp;
texDescr.addressMode[1] = cudaAddressModeClamp;
texDescr.readMode = cudaReadModeElementType;
checkCudaErrors(
cudaCreateTextureObject(&heightFieldTex, &texRes, &texDescr, NULL));
//////////////////////////////////////////////////////////////////////////////
// Ray (starts at origin and traverses the height field diagonally)
Ray ray;
ray.origin = make_float3(0, 0, 2.0f);
int2 dir = make_int2(dim.x - 1, dim.y - 1);
ray.dir = make_float2((float)dir.x, (float)dir.y);
ray.length = max(abs(dir.x), abs(dir.y));
ray.oneOverLength = 1.0f / ray.length;
//////////////////////////////////////////////////////////////////////////////
// View angles
// Allocate view angles for each point along the ray
thrust::device_vector<float> d_angles(ray.length);
// Allocate result of max-scan operation on the array of view angles
thrust::device_vector<float> d_scannedAngles(ray.length);
//////////////////////////////////////////////////////////////////////////////
// Visibility results
// Allocate visibility results for each point along the ray
thrust::device_vector<Bool> d_visibilities(ray.length);
thrust::host_vector<Bool> h_visibilities(ray.length);
thrust::host_vector<Bool> h_visibilitiesRef(ray.length);
//////////////////////////////////////////////////////////////////////////////
// Reference solution
lineOfSight_gold(heightField, ray, (Bool *)&h_visibilitiesRef[0]);
//////////////////////////////////////////////////////////////////////////////
// Device solution
// Execution configuration
dim3 block(256);
dim3 grid((uint)ceil(ray.length / (double)block.x));
// Compute device solution
printf("Line of sight\n");
sdkStartTimer(&timer);
for (uint i = 0; i < numIterations; ++i) {
// Compute view angle for each point along the ray
computeAngles_kernel<<<grid, block>>>(
ray, thrust::raw_pointer_cast(&d_angles[0]), heightFieldTex);
getLastCudaError("Kernel execution failed");
// Perform a max-scan operation on the array of view angles
thrust::inclusive_scan(d_angles.begin(), d_angles.end(),
d_scannedAngles.begin(), thrust::maximum<float>());
getLastCudaError("Kernel execution failed");
// Compute visibility results based on the array of view angles
// and its scanned version
computeVisibilities_kernel<<<grid, block>>>(
thrust::raw_pointer_cast(&d_angles[0]),
thrust::raw_pointer_cast(&d_scannedAngles[0]), ray.length,
thrust::raw_pointer_cast(&d_visibilities[0]));
getLastCudaError("Kernel execution failed");
}
cudaDeviceSynchronize();
sdkStopTimer(&timer);
getLastCudaError("Kernel execution failed");
// Copy visibility results back to the host
thrust::copy(d_visibilities.begin(), d_visibilities.end(),
h_visibilities.begin());
// Compare device visibility results against reference results
bool res = compareData(thrust::raw_pointer_cast(&h_visibilitiesRef[0]),
thrust::raw_pointer_cast(&h_visibilities[0]),
ray.length, 0.0f, 0.0f);
printf("Average time: %f ms\n\n", sdkGetTimerValue(&timer) / numIterations);
sdkResetTimer(&timer);
// Cleanup memory
checkCudaErrors(cudaFreeArray(heightFieldArray));
return res;
}
////////////////////////////////////////////////////////////////////////////////
//! Compute view angles for each point along the ray
//! @param ray ray
//! @param angles view angles
////////////////////////////////////////////////////////////////////////////////
__global__ void computeAngles_kernel(const Ray ray, float *angles,
cudaTextureObject_t HeightFieldTex) {
uint i = blockDim.x * blockIdx.x + threadIdx.x;
if (i < ray.length) {
float2 location = getLocation(ray, i + 1);
float height = tex2D<float>(HeightFieldTex, location.x, location.y);
float angle = getAngle(ray, location, height);
angles[i] = angle;
}
}
////////////////////////////////////////////////////////////////////////////////
//! Compute visibility for each point along the ray
//! @param angles view angles
//! @param scannedAngles max-scanned view angles
//! @param numAngles number of view angles
//! @param visibilities boolean array indicating the visibility of each point
//! along the ray
////////////////////////////////////////////////////////////////////////////////
__global__ void computeVisibilities_kernel(const float *angles,
const float *scannedAngles,
int numAngles, Bool *visibilities) {
uint i = blockDim.x * blockIdx.x + threadIdx.x;
if (i < numAngles) {
visibilities[i] = scannedAngles[i] <= angles[i];
}
}
////////////////////////////////////////////////////////////////////////////////
//! Compute reference data set
//! @param heightField height field
//! @param ray ray
//! @param visibilities boolean array indicating the visibility of each point
//! along the ray
////////////////////////////////////////////////////////////////////////////////
void lineOfSight_gold(const HeightField heightField, const Ray ray,
Bool *visibilities) {
float angleMax = asinf(-1.0f);
for (int i = 0; i < ray.length; ++i) {
float2 location = getLocation(ray, i + 1);
float height =
*(heightField.height + heightField.width * (int)floorf(location.y) +
(int)floorf(location.x));
float angle = getAngle(ray, location, height);
if (angle > angleMax) {
angleMax = angle;
visibilities[i] = True;
} else {
visibilities[i] = False;
}
}
}
////////////////////////////////////////////////////////////////////////////////
//! Compute the 2D coordinates of the point located at i steps from the origin
//! of the ray
//! @param ray ray
//! @param i integer offset along the ray
////////////////////////////////////////////////////////////////////////////////
__device__ __host__ float2 getLocation(const Ray ray, int i) {
float step = i * ray.oneOverLength;
return make_float2(ray.origin.x, ray.origin.y) + ray.dir * step;
}
////////////////////////////////////////////////////////////////////////////////
//! Compute the angle of view between a 3D point and the origin of the ray
//! @param ray ray
//! @param location 2D coordinates of the input point
//! @param height height of the input point
////////////////////////////////////////////////////////////////////////////////
__device__ __host__ float getAngle(const Ray ray, float2 location,
float height) {
float2 dir = location - make_float2(ray.origin.x, ray.origin.y);
return atanf((height - ray.origin.z) / length(dir));
}