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[英]Texture render does not work as verticies but works as classic old opengl code
[英]Why does this OpenGL split screen code work? Unidentified texture?
因此,我有一个可拆分屏幕的OpenGL程序。 经过研究,我的代码如下所示:
glEnable(GL_DEPTH_TEST);
glClear(GL_COLOR_BUFFER_BIT);
// 1
// ----- Camera -----
glViewport(0, 0, _windowW/2, _windowH);
// Tell OpenGL we want to manipulate the projection matrix
glMatrixMode(GL_PROJECTION);
// Undo previous transformations
glLoadIdentity();
// Perspective transformation
gluPerspective(_fov,_asp,_worldSize/_trolly,_trolly*_worldSize);
// Move main camera
_cameraLook[0] = _cameraLoc[0] + Sin(_th1)*Cos(_ph1)*_lookDistance;
_cameraLook[1] = _cameraLoc[1] + Sin(_ph1)*_lookDistance;
_cameraLook[2] = _cameraLoc[2] + Cos(_th1)*Cos(_ph1)*_lookDistance;
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(_cameraLoc[0], _cameraLoc[1], _cameraLoc[2], _cameraLook[0], _cameraLook[1], _cameraLook[2], 0, 1, 0);
// ----- Drawing of scene -----
drawSceneContents();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClear(GL_DEPTH_BUFFER_BIT);
//glBindTexture(GL_TEXTURE_2D,_framebufImg1);
glBegin(GL_QUADS);
glTexCoord2f(0.25, 0.0); glVertex2f(-1.0, -1.0);
glTexCoord2f(0.25, 1.0); glVertex2f(-1.0, +1.0);
glTexCoord2f(0.75, 1.0); glVertex2f(+0.0, +1.0);
glTexCoord2f(0.75, 0.0); glVertex2f(+0.0, -1.0);
glEnd();
// 2
// ----- Camera -----
glViewport(_windowW/2, 0, _windowW/2, _windowH);
// Tell OpenGL we want to manipulate the projection matrix
glMatrixMode(GL_PROJECTION);
// Undo previous transformations
glLoadIdentity();
// Perspective transformation
gluPerspective(_fov,_asp,_worldSize/_trolly,_trolly*_worldSize);
// Move main camera
_cameraLook[0] = _cameraLoc[4] + Sin(_th2)*Cos(_ph2)*_lookDistance;
_cameraLook[1] = _cameraLoc[5] + Sin(_ph2)*_lookDistance;
_cameraLook[2] = _cameraLoc[6] + Cos(_th2)*Cos(_ph2)*_lookDistance;
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(_cameraLoc[4], _cameraLoc[5], _cameraLoc[6], _cameraLook[0], _cameraLook[1], _cameraLook[2], 0, 1, 0);
// ----- Drawing of scene -----
drawSceneContents();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClear(GL_DEPTH_BUFFER_BIT);
//glBindTexture(GL_TEXTURE_2D,_framebufImg1);
glBegin(GL_QUADS);
glTexCoord2f(0.25, 0.0); glVertex2f(-0.0, -1.0);
glTexCoord2f(0.25, 1.0); glVertex2f(-0.0, +1.0);
glTexCoord2f(0.75, 1.0); glVertex2f(+1.0, +1.0);
glTexCoord2f(0.75, 0.0); glVertex2f(+1.0, -1.0);
glEnd();
但是,我不明白为什么它能正常工作,我必须缺少OpenGL可以做的一些基本工作。 我不了解的部分在每个“屏幕”的末尾,在这里我绘制了一个纹理的四边形(最后5行代码)。 但是这种纹理是从哪里来的呢? 为什么它恰好是我为该屏幕绘制的场景的纹理? 我从来没有做过glBindTexture或glEnable(GL_TEXTURE_2D)任何事情,实际上,在所有这些代码之前,我都可以放入glDisable(GL_TEXTURE_2D),并且该代码仍然有效! 怎么样? 除了纹理坐标外,如何在不提及代码的情况下拥有纹理四边形?
编辑 :通过datenwolf进行更正 ,这里已作了详细说明=> 10.视口不会剪切或剪开
根据您的纹理名称( _framebufImg1
), drawSceneContents
应该为FBO实现屏幕外渲染,该FBO应该将纹理作为颜色附件进行附加。
glViewport将投影映射到屏幕的一半宽度,这使您可以在2个不同的位置绘制具有相同顶点的纹理四边形
glViewport(0, 0, _windowW/2, _windowH);
//first pass
glViewport(_windowW/2, 0, _windowW/2, _windowH);
//second pass
没有drawSceneContents
详细信息,我不能说更多...
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