kc3-lang/angle/samples/simple_texture_2d

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• SimpleTexture2D.cpp

• //
  // Copyright 2014 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  
  //            Based on Simple_Texture2D.c from
  // Book:      OpenGL(R) ES 2.0 Programming Guide
  // Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
  // ISBN-10:   0321502795
  // ISBN-13:   9780321502797
  // Publisher: Addison-Wesley Professional
  // URLs:      http://safari.informit.com/9780321563835
  //            http://www.opengles-book.com
  
  #include "SampleApplication.h"
  
  #include "texture_utils.h"
  #include "util/shader_utils.h"
  
  class SimpleTexture2DSample : public SampleApplication
  {
    public:
      SimpleTexture2DSample(int argc, char **argv) : SampleApplication("SimpleTexture2D", argc, argv)
      {}
  
      bool initialize() override
      {
          constexpr char kVS[] = R"(attribute vec4 a_position;
  attribute vec2 a_texCoord;
  varying vec2 v_texCoord;
  void main()
  {
      gl_Position = a_position;
      v_texCoord = a_texCoord;
  })";
  
          constexpr char kFS[] = R"(precision mediump float;
  varying vec2 v_texCoord;
  uniform sampler2D s_texture;
  void main()
  {
      gl_FragColor = texture2D(s_texture, v_texCoord);
  })";
  
          mProgram = CompileProgram(kVS, kFS);
          if (!mProgram)
          {
              return false;
          }
  
          // Get the attribute locations
          mPositionLoc = glGetAttribLocation(mProgram, "a_position");
          mTexCoordLoc = glGetAttribLocation(mProgram, "a_texCoord");
  
          // Get the sampler location
          mSamplerLoc = glGetUniformLocation(mProgram, "s_texture");
  
          // Load the texture
          mTexture = CreateSimpleTexture2D();
  
          glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
  
          mTimer.start();
  
          return true;
      }
  
      void destroy() override
      {
          glDeleteProgram(mProgram);
          glDeleteTextures(1, &mTexture);
      }
  
      void draw() override
      {
          GLfloat vertices[] = {
              -0.5f, 0.5f,  0.0f,  // Position 0
              0.0f,  0.0f,         // TexCoord 0
              -0.5f, -0.5f, 0.0f,  // Position 1
              0.0f,  1.0f,         // TexCoord 1
              0.5f,  -0.5f, 0.0f,  // Position 2
              1.0f,  1.0f,         // TexCoord 2
              0.5f,  0.5f,  0.0f,  // Position 3
              1.0f,  0.0f          // TexCoord 3
          };
          GLushort indices[] = {0, 1, 2, 0, 2, 3};
  
          // Set the viewport
          glViewport(0, 0, getWindow()->getWidth(), getWindow()->getHeight());
  
          // Clear the color buffer
          glClear(GL_COLOR_BUFFER_BIT);
  
          // Use the program object
          glUseProgram(mProgram);
  
          // Load the vertex position
          glVertexAttribPointer(mPositionLoc, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), vertices);
          // Load the texture coordinate
          glVertexAttribPointer(mTexCoordLoc, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat),
                                vertices + 3);
  
          glEnableVertexAttribArray(mPositionLoc);
          glEnableVertexAttribArray(mTexCoordLoc);
  
          // Bind the texture
          glActiveTexture(GL_TEXTURE0);
          glBindTexture(GL_TEXTURE_2D, mTexture);
  
          // Set the texture sampler to texture unit to 0
          glUniform1i(mSamplerLoc, 0);
  
          glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
  
          mDrawCount++;
  
          if (mDrawCount % 100 == 0)
          {
              printf("Rate: %0.2lf iterations / second\n",
                     static_cast<double>(mDrawCount) / mTimer.getElapsedTime());
          }
      }
  
    private:
      // Handle to a program object
      GLuint mProgram;
  
      // Attribute locations
      GLint mPositionLoc;
      GLint mTexCoordLoc;
  
      // Sampler location
      GLint mSamplerLoc;
  
      // Texture handle
      GLuint mTexture;
  
      Timer mTimer;
      uint32_t mDrawCount = 0;
  };
  
  int main(int argc, char **argv)
  {
      SimpleTexture2DSample app(argc, argv);
      return app.run();
  }