Texture mapping without OpenGL involves applying a 2D image, known as a texture, onto a 3D model to enhance its visual appearance.
To achieve texture mapping, you'll need to store texture coordinates (U, V) for each vertex of your 3D model. These coordinates define the position on the texture that corresponds to that particular vertex.
During rasterization, you'll need to interpolate the texture coordinates for each pixel within a triangle. This interpolation process ensures a smooth transition of the texture across the triangle's surface.
Once you have the interpolated texture coordinates for a pixel, you can use them to sample the texture image and retrieve the corresponding color value. This color value is then used to shade the pixel.
Below is an example code snippet that demonstrates texture mapping without OpenGL using C++:
struct Vertex {
float x, y, z;
float u, v; // Texture coordinates
};
struct Triangle {
Vertex v1, v2, v3;
};
void DrawTriangle(Triangle triangle, Image texture) {
// Calculate the bounding box of the triangle
float minX = min(triangle.v1.x, min(triangle.v2.x, triangle.v3.x));
float maxX = max(triangle.v1.x, max(triangle.v2.x, triangle.v3.x));
float minY = min(triangle.v1.y, min(triangle.v2.y, triangle.v3.y));
float maxY = max(triangle.v1.y, max(triangle.v2.y, triangle.v3.y));
// Loop through each pixel within the bounding box
for (int x = minX; x <= maxX; x++) {
for (int y = minY; y <= maxY; y++) {
// Check if the pixel is inside the triangle
if (IsInsideTriangle(x, y, triangle)) {
// Calculate the interpolated texture coordinates for the pixel
float u = InterpolateTextureCoordinate(x, y, triangle);
float v = InterpolateTextureCoordinate(x, y, triangle);
// Sample the texture image using the interpolated texture coordinates
Color color = SampleTexture(u, v, texture);
// Set the pixel color
SetPixelColor(x, y, color);
}
}
}
}
By following this procedure, you can achieve texture mapping without the use of OpenGL.