cpp-game-engine/graphics/src/opengl_helper.cxx

//
//  helper.cxx
//  graphics
//
//  Created by Sam Jaffe on 5/18/19.
//  Copyright © 2019 Sam Jaffe. All rights reserved.
//

#include "helper.hpp"

#ifdef __APPLE__
#include <OpenGL/gl3.h>
#endif

#include "vector/vector.hpp"

namespace graphics { namespace textures {
  static int glfmt(format color_fmt) {
    switch (color_fmt) {
    case format::RGB:
      return GL_RGB;
    case format::RGBA:
      return GL_RGBA;
    }
  }

  unsigned int init(format color_fmt, math::vec2i dimension,
                    unsigned char * data) {
    unsigned int id;
    // Enable texturings
    //    glEnable( GL_TEXTURE_2D );

    // Tell OpenGL that our pixel data is single-byte aligned
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    // Ask OpenGL for an unused texName (ID number) to use for this texture
    glGenTextures(1, &id);

    // Tell OpenGL to bind (set) this as the currently active texture
    glBindTexture(GL_TEXTURE_2D, id);
    // Set texture clamp vs. wrap (repeat)

    // one of: GL_CLAMP_TO_EDGE, GL_REPEAT, GL_MIRRORED_REPEAT,
    // GL_MIRROR_CLAMP_TO_EDGE, ...
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    // the format our source pixel data is currently in; any of: GL_RGB,
    // GL_RGBA, GL_LUMINANCE, GL_LUMINANCE_ALPHA, ...
    int bufferFormat = glfmt(color_fmt);

    // the format we want the texture to me on the card; allows us to translate
    // into a different texture format as we upload to OpenGL
    int internalFormat = bufferFormat;

    /* glTexImage2D: Load a 2d texture image
     * target: Creating this as a 2d texture.
     * level: Which mipmap level to use as the "root" (0 = the highest-quality,
     *  full-res image), if mipmaps are enabled.
     * internalFormat: Type of texel format we want OpenGL to use for this
     *  texture internally on the video card.
     * width: Texel-width of image; for maximum compatibility, use 2^N + 2^B,
     *  where N is some integer in the range [3,10], and B is the border
     *  thickness [0,1]
     * height: Texel-height of image; for maximum compatibility, use 2^M + 2^B,
     *  where M is some integer in the range [3,10], and B is the border
     *  thickness [0,1]
     * border: Border size, in texels (must be 0 or 1)
     * format: Pixel format describing the composition of the pixel data in
     *  buffer
     * type: Pixel color components are unsigned bytes (one byte per color/alpha
     *  channel)
     * pixels: Location of the actual pixel data bytes/buffer
     */
    glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, dimension.x(), dimension.y(),
                 0, bufferFormat, GL_UNSIGNED_BYTE, data);

    glGenerateMipmap(GL_TEXTURE_2D);

    // Set magnification (texel > pixel) and minification (texel < pixel)
    // filters one of: GL_NEAREST, GL_LINEAR
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    // one of: GL_NEAREST, GL_LINEAR, GL_NEAREST_MIPMAP_NEAREST,
    // GL_NEAREST_MIPMAP_LINEAR, GL_LINEAR_MIPMAP_NEAREST,
    // GL_LINEAR_MIPMAP_LINEAR
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                    GL_NEAREST_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 5);

    return id;
  }
}}

namespace graphics { namespace shaders {
  unsigned int init(unsigned int type, std::string const & path) { return 0; }
}}