我们很难用framebuffer对象计算渲染到纹理。我们成功了 将纹理绘制到另一个纹理,但纹理不居中。
如果我们将纹理大小设置为与窗口大小相对应,则它是居中的,但我们希望能够管理较小的纹理。
GLuint texture[3];
unsigned int fbo;
SDL_Surface *TextureImage[1];
int LoadGLTextures( )
{
/* Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit */
if ( ( TextureImage[0] = SDL_LoadBMP( "crate.bmp" ) ) )
{
/* Create The Texture */
glGenTextures( 1, &texture[0] );
/* Typical Texture Generation Using Data From The Bitmap */
glBindTexture( GL_TEXTURE_2D, texture[0] );
/* Generate The Texture */
glTexImage2D( GL_TEXTURE_2D, 0, 3, TextureImage[0]->w,
TextureImage[0]->h, 0, GL_BGR,
GL_UNSIGNED_BYTE, TextureImage[0]->pixels );
/* Linear Filtering */
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
}
/* Free up any memory we may have used */
if ( TextureImage[0] )
//SDL_FreeSurface( TextureImage[0] );
return 1;
}
void initFrameBufferTexture(void) {
glGenTextures(1, &texture[1]); // Generate one texture
glBindTexture(GL_TEXTURE_2D, texture[1]); // Bind the texture fbo_texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, TextureImage[0]->w, TextureImage[0]->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard texture with the width and height of our window
// Setup the basic texture parameters
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
//glGenerateMipmapEXT(GL_TEXTURE_2D);
// Unbind the texture
glBindTexture(GL_TEXTURE_2D, 0);
}
void initFrameBuffer(void) {
initFrameBufferTexture(); // Initialize our frame buffer texture
glGenFramebuffersEXT(1, &fbo); // Generate one frame buffer and store the ID in fbo
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo); // Bind our frame buffer
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, texture[1], 0); // Attach the texture fbo_texture to the color buffer in our frame buffer
GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT); // Check that status of our generated frame buffer
if (status != GL_FRAMEBUFFER_COMPLETE_EXT) // If the frame buffer does not report back as complete
{
exit(0); // Exit the application
}
//glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); // Unbind our frame buffer
}
int main(int argc, char *argv[])
{
gfx_manager.init(640, 480, 32);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.375f, 0.375f, 0);
glClearColor(0.3, 0.3, 0.3, 0);
glClear(GL_COLOR_BUFFER_BIT);
LoadGLTextures();
initFrameBuffer();
glMatrixMode(GL_TEXTURE);
glGenFramebuffersEXT(1, &fbo);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glPushAttrib(GL_VIEWPORT_BIT);
//glGenerateMipmapEXT();
//glOrtho(0, TextureImage[0]->w, TextureImage[0]->h, 0, 0, 1);
//glViewport(0, 0, TextureImage[0]->w, TextureImage[0]->h);
glClearColor (0.0f, 0.0f, 1.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glBegin( GL_QUADS ); /* Draw A Quad */
glTexCoord2f(0.0f, 0.0f);glVertex2f(0.0f, 0.0f);
glTexCoord2f(1.0f, 0.0f);glVertex2f(0.0f + TextureImage[0]->w , 0.0f);
glTexCoord2f(1.0f, 1.0f);glVertex2f(0.0f + TextureImage[0]->w, 0.0f + TextureImage[0]->h);
glTexCoord2f(0.0f, 1.0f);glVertex2f(0.0f, 0.0f + TextureImage[0]->h);
glEnd( );
glPopAttrib();
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
glLoadIdentity();
glClearColor (0.0f, 0.0f, 1.0f, 1.0f);
glBindTexture(GL_TEXTURE_2D, texture[1]);
glLoadIdentity();
glBegin( GL_QUADS ); /* Draw A Quad */
glTexCoord2f(0.0f, 0.0f);glVertex2f(300.0f, 200.0f);
glTexCoord2f(0.0f, 1.0f);glVertex2f(300.0f , 200.0f + TextureImage[0]->h);
glTexCoord2f(1.0f, 1.0f);glVertex2f(300.0f + TextureImage[0]->w, 200.0f + TextureImage[0]->h);
glTexCoord2f(1.0f, 0.0f);glVertex2f(300.0f + TextureImage[0]->w, 200.0f);
glEnd( );
SDL_GL_SwapBuffers( );
sleep(100);
return 0;
}
答案 0 :(得分:3)
您可能已将矩阵和视口设置为与窗口大小相匹配。在绘制之前,请确保将它们更改为适合帧缓冲区大小的值。