[osg-users] [HELP] Properly using osg::VertexAttribDivisor for basic geometry instancing

[Julien Valentin]

Hi Werner
vertex attribute pulling (your method) has good perf since number of instances stay low. However with growing number of instances you would see the perf diff compared to vertex attribute.
(I saw benchmark on a youtube nvidia speech but don't remember where)
No, using attrib divisor is still a better approach for perf perspective...
Cheers



wernerM wrote:
> Hi,
> 
> what we do is packing our instance parameters in a uniform array and access it via gl_InstanceID as an index into the array.
> 
> - Werner -
> 
> Am 01.08.2018 um 16:32 schrieb Julien Valentin:
> 
> 
> >  
> > > Hi
> > > perhaps it's because of transaltion array 's default binding (UNDEFINED)
> > > try
> > > translation->setArrayBinding(Array::PER_VERTEX)
> > > Cheers
> > > 
> > > 
> > > ppsychrite wrote:
> > > 
> > > > hello sorry if i did this wrong but i dont know how to use mailing lists
> > > > 
> > > > so ive been trying to do modern glsl/opengl 3.3+ with osg::Geometry and 
> > > > osg::Stateset and it's been working OK for basic triangle except for 
> > > > implementing instanced array data
> > > > am I doing it the wrong way? here's the .cpp code for it and for me it 
> > > > seems well enough and fine, position and color works fine
> > > > 
> > > > 
> > > > 	osg::Vec3 coords[] = {
> > > > 		{ -0.05f,0.05f,0.f },
> > > > 		{ 0.05f,-0.05f,0.f },
> > > > 		{ 0.05f,0.05f,1.f }
> > > > 	};
> > > > 	osg::Vec3 colors[] = {
> > > > 		{1.f,0.f,0.f},
> > > > 		{0.f,1.f,0.f},
> > > > 		{0.f,0.f,1.f}
> > > > 	};
> > > > 
> > > > 	osg::Vec2 instancetranslations[] = {
> > > > 		{ 0.0f, 0.0f },
> > > > 		{ 0.1f, 0.0f },
> > > > 		{ 0.2f, 0.0f }
> > > > 	};
> > > > 
> > > > 	osg::Vec3Array *pos = new osg::Vec3Array(sizeof(coords) / 
> > > > sizeof(osg::Vec3), coords);
> > > > 	osg::Vec3Array *color = new osg::Vec3Array(sizeof(colors) / 
> > > > sizeof(osg::Vec3), colors);
> > > > 	osg::Vec2Array *translation = new 
> > > > osg::Vec2Array(sizeof(instancetranslations) / sizeof(osg::Vec2), 
> > > > instancetranslations);
> > > > 
> > > > 	osg::Geometry *vao = new osg::Geometry();
> > > > 	vao->setUseDisplayList(false);
> > > > 	vao->setUseVertexArrayObject(true);
> > > > 	vao->setUseVertexBufferObjects(true);
> > > > 
> > > > 	vao->setVertexAttribArray(0, pos, osg::Array::BIND_PER_VERTEX);
> > > > 	vao->setVertexAttribArray(1, color, osg::Array::BIND_PER_VERTEX);
> > > > 	vao->setVertexAttribArray(2, translation);
> > > > 
> > > > 	vao->addPrimitiveSet(new osg::DrawArrays(GL_TRIANGLES, 0, 3, 3)); //3 
> > > > instances
> > > > 
> > > > 	osg::ref_ptr<osg::Program> program = new osg::Program;
> > > > 
> > > > 	program->addShader(osgDB::readShaderFile("shaders/basic.vert"));
> > > > 	program->addShader(osgDB::readShaderFile("shaders/basic.frag"));
> > > > 
> > > > 	osg::StateSet *stateset = geom->getOrCreateStateSet();
> > > > 	stateset->setAttributeAndModes(program.get());
> > > > 	stateset->setAttribute(new osg::VertexAttribDivisor(2, 1)); //set 3rd 
> > > > array as per-instance
> > > > 
> > > > here's the vertex shader code for it:
> > > > 
> > > > 
> > > > #version 330 core
> > > > layout (location = 0) in vec3 aPos;
> > > > layout (location = 1) in vec3 aColor;
> > > > layout (location = 2) in vec2 aTrans;
> > > > 
> > > > out vec3 color;
> > > > 
> > > > void main()
> > > > {
> > > > color = aColor;
> > > > gl_Position = vec4(aPos.x+ aTrans.x,aPos.y+ aTrans.y,aPos.z,1.0);
> > > > }
> > > > 
> > > > 
> > > > aTrans doesn't move the triangle at all, it's just one. I know it isn't 
> > > > the shaders fault because instead of adding aTrans to aPos I've done 
> > > > (gl_InstanceID * 0.1f) and it's worked perfectly, seeing 3 instanced 
> > > > triangles
> > > > 
> > > > what am i doing wrong/how could i get per-instanced array working?
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > _______________________________________________
> > > > osg-users mailing list
> > > > 
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