请教：用两个Rtt相机渲染到同一个纹理对象，深度应该怎么处理

usr1

用两个Rtt相机渲染到同一个纹理对象，深度应该怎么处理，修改了osgexample里面的prerender例子，场景结构如下：
           | new texture2D texture
root--- |-camera0  prerender, clearmask(color|depth),attach COLOR_BUFFER to texture,   DO_NOT_COMPUTE_NEAR_FAR
           |-camera1  prerender, clearmask(0), attach COLOR_BUFFER to the same texture,  DO_NOT_COMPUTE_NEAR_FAR
           |-geode,   use the prerendered texture2D by camera0 and camera1 as texture unit 0.
第一个rtt相机渲染了飞机，第二个rtt相机渲染了牛，加了深度测试和深度写，但是效果始终不对，后一个相机渲染的内容会覆盖前一个相机渲染的内容，并没有进行深度测试。
请问：这种情况下，深度应该怎么处理呢？

完整代码在附件 osgprerender.cpp (10.4 KB, 下载次数: 1)

2013-6-19 11:09 上传

点击文件名下载附件 ，创建两个rtt的代码如下
// then create the camera node to do the render to texture
        {   
                osg::Camera* camera = new osg::Camera;

                // set up the background color and clear mask.
                camera->setClearColor(osg::Vec4(0.1f,0.1f,0.3f,1.0f));
                camera->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
                camera->setComputeNearFarMode(osg::Camera:O_NOT_COMPUTE_NEAR_FAR);

                const osg::BoundingSphere& bs = subgraph->getBound();
                if (!bs.valid())
                {
                        return subgraph;
                }

                float znear = 1.0f*bs.radius();
                float zfar  = 3.0f*bs.radius();

                // 2:1 aspect ratio as per flag geometry below.
                float proj_top   = 0.25f*znear;
                float proj_right = 0.5f*znear;

                znear *= 0.9f;
                zfar *= 1.1f;

                // set up projection.
                camera->setProjectionMatrixAsFrustum(-proj_right,proj_right,-proj_top,proj_top,znear,zfar);

                // set view
                camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
                camera->setViewMatrixAsLookAt(bs.center()-osg::Vec3(0.0f,2.0f,0.0f)*bs.radius(),bs.center(),osg::Vec3(0.0f,0.0f,1.0f));

                // set viewport
                camera->setViewport(0,0,tex_width,tex_height);

                // set the camera to render before the main camera.
                camera->setRenderOrder(osg::Camera:RE_RENDER);

                // tell the camera to use OpenGL frame buffer object where supported.
                camera->setRenderTargetImplementation(renderImplementation);


                if (useImage)
                {
                        osg::Image* image = new osg::Image;
                        //image->allocateImage(tex_width, tex_height, 1, GL_RGBA, GL_UNSIGNED_BYTE);
                        image->allocateImage(tex_width, tex_height, 1, GL_RGBA, GL_FLOAT);

                        // attach the image so its copied on each frame.
                        camera->attach(osg::Camera::COLOR_BUFFER, image,
                                samples, colorSamples);
                        texture->setImage(0, image);
                }
                else
                {
                        // attach the texture and use it as the color buffer.
                        camera->attach(osg::Camera::COLOR_BUFFER, texture,
                                0, 0, false,
                                samples, colorSamples);
                }


                // add subgraph to render
                camera->addChild(subgraph);

                parent->addChild(camera);

        }  

        //////////////////////////////////////////////////////////////////////////
        // add second rtt camera render "cow.osg" to the texture that has been render with "cessna.osgt"
        // the second camera attch the same texture2D which the first rtt camera has attached.
        //////////////////////////////////////////////////////////////////////////
        {   
                osg::Camera* camera = new osg::Camera;

                // set up the background color and clear mask.
                camera->setClearColor(osg::Vec4(0.1f,0.1f,0.3f,1.0f));
                camera->setClearMask(/*GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT*/0);
                camera->setComputeNearFarMode(osg::Camera::DO_NOT_COMPUTE_NEAR_FAR);
                osg::ref_ptr<osg::Node> cow = osgDB::readNodeFile("cow.osg");

                const osg::BoundingSphere& bs = subgraph->getBound();
                if (!bs.valid())
                {
                        return subgraph;
                }

                float znear = 1.0f*bs.radius();
                float zfar  = 3.0f*bs.radius();

                // 2:1 aspect ratio as per flag geometry below.
                float proj_top   = 0.25f*znear;
                float proj_right = 0.5f*znear;

                znear *= 0.9f;
                zfar *= 1.1f;

                // set up projection.
                camera->setProjectionMatrixAsFrustum(-proj_right,proj_right,-proj_top,proj_top,znear,zfar);

                // set view
                camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
                camera->setViewMatrixAsLookAt(bs.center()-osg::Vec3(0.0f,2.0f,0.0f)*bs.radius(),bs.center(),osg::Vec3(0.0f,0.0f,1.0f));

                // set viewport
                camera->setViewport(0,0,tex_width,tex_height);

                // set the camera to render before the main camera.
                camera->setRenderOrder(osg::Camera::PRE_RENDER);

                // tell the camera to use OpenGL frame buffer object where supported.
                camera->setRenderTargetImplementation(renderImplementation);


                if (useImage)
                {
                        osg::Image* image = new osg::Image;
                        //image->allocateImage(tex_width, tex_height, 1, GL_RGBA, GL_UNSIGNED_BYTE);
                        image->allocateImage(tex_width, tex_height, 1, GL_RGBA, GL_FLOAT);

                        // attach the image so its copied on each frame.
                        camera->attach(osg::Camera::COLOR_BUFFER, image,
                                samples, colorSamples);
                        texture->setImage(0, image);
                }
                else
                {
                        // attach the texture and use it as the color buffer.
                        camera->attach(osg::Camera::COLOR_BUFFER, texture,
                                0, 0, false,
                                samples, colorSamples);
                }


                // add subgraph to render
                camera->addChild(cow);

                parent->addChild(camera);

        }   

array

您的意思是您把同一个纹理同时用作两个RTT的Target？不允许这么做，您可以考虑用两个纹理作为Quad的两个纹理通道的输入，然后再用TexEnv合并