More Textures

• I found these two tutorials helpful
  • Texturing With Images
  • Textures Objecs and Parameters This one helps with all the variations of parameters..
• Shader Language Textures
  • No change really,
  • Texture coordinates need to be included in the data as before.

  • vertexT BillboardData[6] = {
         // x     y    z    r    g    b       nx   ny   nz    s    t
        {{ -1.0, 0.0, 0.0}, {0.0, 0.0, 0.0}, {0.0, 1.0, 0.0},{0.0, 0.0}},
        {{ 1.0, 0.0, 0.0}, {0.0, 0.0, 0.0}, {0.0, 1.0, 0.0}, {1.0, 0.0}},
    	

  • The texture loading from before works just fine

    void BillboardClass::LoadTexture() {
       BitMapFile *image[1];
       image[0] = getbmp("tree1.bmp");
    
       glGenTextures(1, Textures);
       glBindTexture(GL_TEXTURE_2D, Textures[0]);
    
       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image[0]->sizeX,
               image[0]->sizeY, 0, GL_RGBA, GL_UNSIGNED_BYTE, image[0]->data);
    
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    
       float color[] = { 1.0f, 1.0f, 1.0f, 1.0f };
       glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, color);
    
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    
       glGenerateMipmap(GL_TEXTURE_2D);
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                        GL_NEAREST_MIPMAP_NEAREST);
    
       return;
    }
    
    	

    • GL_REPEAT The integer part of the coordinate will be ignored and a repeating pattern is formed. (A mod operation)
    • GL_CLAMP_TO_BORDER means coordinates outside of the range (s,t 0-1) will be given the border color.
    • And this is set in the next command.
    • GL_CLAMP_TO_EDGE means that the coordinates outside will be set to the values at the edge of the texmap
    • GL_MIRRORED_REPEAT The texture will also be repeated, but it will be mirrored when the integer part of the coordinate is odd.
  • I use a mipmap here as well
    • void glGenerateMipmap( GLenum target);
      • GL_TEXTURE_2D or others
      • It is applied to the bound target.
    • We can play with this in the landscape.
    • GL_TEXTURE_MIN_FILTER
      • GL_{NEAREST,LINEAR}_MIPMAP_{NEAREST,LINEAR}
      • ALSO GL_NEAREST, GL_LINEAR
    • GL_TEXTURE_MAG_FILTER only LINEAR and NEAREST
• When Drawing:

  • glBindVertexArray(VAOs[0]);
    glBindTexture(GL_TEXTURE_2D, Textures[0]);
    glDrawArrays(GL_TRIANGLES, 0, 6)
    	

  • There is no need to enable textures, but you must chagne the vertex shader.

    varying vec4 color;
    varying vec2 Texcoord;
    
    uniform sampler2D tex;
    uniform int UseTexture;
    
    void main() {
        vec4 tmp;
    
        tmp =   texture2D(tex, Texcoord);
    
        if (UseTexture == 0) {
            gl_FragColor =  color;
        } else if (UseTexture == 2) {
            if (tmp.rgb  == vec3(1.0, 1.0, 1.0) ) {
                discard;
            }
            gl_FragColor =  tmp;
        } else {
            gl_FragColor =  tmp;
        }
    }