OSG 3.4.0
I am trying to use "instancing" (starting from the example osgdrawinstanced) to
draw simple square geometry at multiple locations.
I am getting all of my instances sitting on top of each other at (0,0,0). That
is they are not offset to their expected locations.
I know my shader is working OK because if I add a hack to my shader to add in
an offset that depends on gl_InstanceID then the squares do get "offset" per
instance.
Step 1
Add "nInstances" of the square to my osg::Geometry
geom.addPrimitiveSet( new osg::DrawArrays( GL_QUADS, 0, 4, nInstances ) );
Step 2
Create a simple shader program that uses an attribute array of offsets ("d") to
offset the vertex locations
std::string vertexSource =
"#version 120\n"
"#extension GL_EXT_draw_instanced : enable\n"
"in vec3 d;\n"
"void main() \n"
"{ \n"
// Use the =coord to translate the position of the vertices.
"vec3 pos = vec3(gl_Vertex) + d;\n"
"vec4 finalPos = vec4(pos, 1.0);\n"
"gl_Position = gl_ModelViewProjectionMatrix *
finalPos;\n"
"} \n";
osg::ref_ptr< osg::Shader > vertexShader = new osg::Shader();
vertexShader->setType(osg::Shader::VERTEX);
vertexShader->setShaderSource(vertexSource);
osg::ref_ptr< osg::Program > program = new osg::Program();
program->addShader(vertexShader.get());
ss->setAttribute(program.get(),osg::StateAttribute::ON);
program->addBindAttribLocation("d", 1);
Step 3
Create an array of offsets 4 * nInstances that contain the offsets for
each vertex. Is this where I am going wrong??? I have checked that "d" is not
(0,0,0) and is varying for each instance. It seems to be that all the instances
are using the same offset.
osg::Vec3Array *attrib = new osg::Vec3Array;
size_t vecIndex = 0;
for (size_t i = 0; i < nInstances ; i++) {
osg::Vec3 d=GetOffSetForInstance(i);
attrib->push_back(d);
attrib->push_back(d);
attrib->push_back(d);
attrib->push_back(d);
}
geom->setVertexAttribArray(1, attrib);
geom->setVertexAttribBinding(1,
osg::Geometry::BIND_PER_VERTEX);
Andrew
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=69743#69743
_______________________________________________
osg-users mailing list
[email protected]
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
