OpenCL Procedural Terrain (Demo)

Using OpenCL to generate a terrain heightmap on the GPU, using the Diamond-Square algorithm.

Made for an IGAD class on GPU programming.

Sample code

OpenCL code to generate the heightmap using the Diamond-Square algorithm, by modifying the y position values of a 2D grid of vertices.

This code is called for every pass of the Diamond-Square algorithm: starting with a rectangle covering the whole terrain, then subdividing that into four smaller rectangles, then subdividing each rectangle again, etc. until the rectangles too small (2*2 vertices).

					
					      #include "tools/random.h" //rng library

                                              #include "opencl_shared.h" //define INTENSITY, SQUARE_SIZE

					      __constant const float Intensity  = 1.0f * INTENSITY;

					      __constant const float CIntensity = 0.25f * INTENSITY;

					      __kernel void task( __global float* vertexBuffer , int rectSize, int randseed )

					      {

					          int idx = get_global_id( 0 ); //x index of the current rectangle

					        	int idz = get_global_id( 1 ); //z index of the current rectangle

					        	rngstate rng;

					        	rngseed( &rng, randseed + idx + SQUARE_SIZE * idy, 1 );

					        	int x1 = (idx * (rectSize-1)) % SQUARE_SIZE;

					        	int x2 = (x1 + rectSize - 1) % SQUARE_SIZE;

					        	int z1 = (idz * (rectSize-1)) % SQUARE_SIZE;

					        	int z2 = (z1 + rectSize - 1) % SQUARE_SIZE;

					        	int centerX = (x1 + x2) / 2;

					        	int centerY = (z1 + z2) / 2;

					        	float IntensityModifier = (float)rectSize/SQUARE_SIZE;

					        	//Diamond step

					        	float NorthWest = vertexBuffer[(y1*SQUARE_SIZE+x1)*3+1]; //nw

					        	float NorthEast = vertexBuffer[(y2*SQUARE_SIZE+x2)*3+1]; //ne

					        	float SouthEast = vertexBuffer[(y1*SQUARE_SIZE+x2)*3+1]; //se

					        	float SouthWest = vertexBuffer[(y2*SQUARE_SIZE+x1)*3+1]; //sw

					        	float Center = ((NorthWest + NorthEast + SouthEast + SouthWest)/4.0f) + (-0.5f + rngfloat(&rng)) * CIntensity * IntensityModifier;

					        	//set height of center vertex

					        	vertexBuffer[(centerZ*SQUARE_SIZE+centerX)*3+1] = Center;

					        	//Square step

					        	float North = ((NorthWest+NorthEast)/2.0f) + (-0.5f + rngfloat(&rng)) * Intensity * IntensityModifier;

					        	float South = ((SouthWest+SouthEast)/2.0f) + (-0.5f + rngfloat(&rng)) * Intensity * IntensityModifier;

					        	float West  = ((NorthWest+SouthWest)/2.0f) + (-0.5f + rngfloat(&rng)) * Intensity * IntensityModifier;

					        	float East  = ((NorthEast+SouthEast)/2.0f) + (-0.5f + rngfloat(&rng)) * Intensity * IntensityModifier;

					        	//set height of vertices

					        	vertexBuffer[(z1*SQUARE_SIZE+centerX)*3+1] = North; //n

					        	vertexBuffer[(z2*SQUARE_SIZE+centerX)*3+1] = South; //s

					        	vertexBuffer[(centerZ*SQUARE_SIZE+x1)*3+1] = West; //w

					        	vertexBuffer[(centerZ*SQUARE_SIZE+x2)*3+1] = East; //e

					      }

Details

Date: 2014-2015
System: PC
Engine: Own engine
Language(s): C++
Dev time: 7 weeks
Solo project
Tag: School

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Wout van Poppel Generalist Game Programmer