Hallo,I want to simulate laser scanner using osg camera. In Fragment shader the color information is converted into position information. And then the position information is accessed from this Fragment to be used to draw points in a view. But the points are not so accurate, as it is shown in the attached picture, which is composed of 11 cameras. The important codes are:
osg::Program * program = new osg::Program();
program->addShader(osg::Shader::readShaderFile(osg::Shader::FRAGMENT,
fragmentShaderPath));
program->addShader(osg::Shader::readShaderFile(osg::Shader::VERTEX,
vertexShaderPath));
osg::Image * image = new osg::Image();
image->allocateImage(xRes, yRes, 1, GL_RGBA,
GL_FLOAT);
osg::ref_ptr<osg::CameraNode> camera(new osg::CameraNode()); camera->setComputeNearFarMode(osg::Camera::DO_NOT_COMPUTE_NEAR_FAR);
camera->setViewport(0, 0, xRes, yRes);
camera->setClearColor(osg::Vec4(1000.0f, 1000.0f,
1000.0f, 1000.0f));
camera->setClearMask(GL_COLOR_BUFFER_BIT |
GL_DEPTH_BUFFER_BIT);
camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
camera->setProjectionMatrixAsFrustum(-tan(
viewYaw), tan(viewYaw), -tan(viewPitch), tan(viewPitch), zNear,zFar);
camera->setViewMatrix(osg::Matrix::lookAt(osg::Vec3d(0, 0, 1.0f),
osg::Vec3d(-10.0f, 0.0f, 0), osg::Vec3d(0, 0, 1)));
camera->setRenderOrder(osg::CameraNode::PRE_RENDER);
camera->setRenderTargetImplementation(renderTargetImplementation);
camera->attach(osg::CameraNode::COLOR_BUFFER,
image);
camera->getOrCreateStateSet()->setAttribute(program,
osg::StateAttribute::ON);
In vertex Shader, I write:
void main()
{
x=(gl_ModelViewMatrix * (gl_Vertex - vec4(0.0,0.0,0.0,0.0))).x;
y=(gl_ModelViewMatrix * (gl_Vertex - vec4(0.0,0.0,0.0,0.0))).y;
z=(gl_ModelViewMatrix * (gl_Vertex - vec4(0.0,0.0,0.0,0.0))).z;
gl_Position = ftransform();
}
in Fragment shader, I write:
gl_FragColor = vec4(abs(z/100),abs(x/17),abs(y/4),0.2);
And I when get the position information, I will multiply them with the
corresponding factors.
However, the points are not that accurate. I seems that the Fragment shader does not calculate the point one by one, but assign a certain value to a certain amount of points.
Can anybody give some advice? Thanks in advance! Shuiying
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