main loop - Page 391 - Developer IT

In GLSL is it possible to offset vertices based on height map colour?

- by Rob

I am attempting to generate some terrain based upon a heightmap. I have generated a 32 x 32 grid and a corresponding height map - In my vertex shader I am trying to offset the position of the Y axis based upon the colour of the heightmap, white vertices being higher than black ones. //Vertex Shader Code #version 330 uniform mat4 modelMatrix; uniform mat4 viewMatrix; uniform mat4 projectionMatrix; uniform sampler2D heightmap; layout (location=0) in vec4 vertexPos; layout (location=1) in vec4 vertexColour; layout (location=3) in vec2 vertexTextureCoord; layout (location=4) in float offset; out vec4 fragCol; out vec4 fragPos; out vec2 fragTex; void main() { // Retreive the current pixel's colour vec4 hmColour = texture(heightmap,vertexTextureCoord); // Offset the y position by the value of current texel's colour value ? vec4 offset = vec4(vertexPos.x , vertexPos.y + hmColour.r, vertexPos.z , 1.0); // Final Position gl_Position = projectionMatrix * viewMatrix * modelMatrix * offset; // Data sent to Fragment Shader. fragCol = vertexColour; fragPos = vertexPos; fragTex = vertexTextureCoord; } However the code I have produced only creates a grid with none of the y vertices higher than any others. This is the C++ code that generates the grid and texture co-orientates which I believe to be correct as the texture is mapped to the grid, hence the white blob in the middle. The grid-lines are generated in the fragment shader, sorry for any confusion. I have tried multiplying the r value of hmColour by 1000 unfortunately that had no effect. The only other problem it could be is that the texture coordinate data is incorrect ? for (int z = 0; z < MAP_Z ; z++) { for(int x = 0; x < MAP_X ; x++) { //Generate Vertex Buffer vertexData[iVertex++] = float (x) * MAP_X; vertexData[iVertex++] = 0; vertexData[iVertex++] = -(float) (z) * MAP_Z; //Colour Buffer NOT NEEDED colourData[iColour++] = 255.0f; // R colourData[iColour++] = 1.0f; // G colourData[iColour++] = 0.0f; // B //Texture Buffer textureData[iTexture++] = (float ) x * (1.0f / MAP_X); textureData[iTexture++] = (float ) z * (1.0f / MAP_Z); } } The heightmap texture I am trying to use appears like so (without grid-lines). This is the corresponding fragment shader // Fragment Shader Code #version 330 uniform sampler2D hmTexture; layout (location=0) out vec4 fragColour; in vec2 fragTex; in vec4 pos; void main(void) { vec2 line = fragTex * 32; // Without Gridlines fragColour = texture(hmTexture,fragTex); // With grid lines // + mix(vec4(0.0, 0.0, 1.0, 0.0), vec4(1.0, 1.0, 1.0, 1.0), // smoothstep(0.05,fract(line.y), 0.99) * smoothstep(0.05,fract(line.x),0.99)); }

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