> Use of glsl in osg is pretty straitforward.
Thanks for the hints so far.
I condensed osgshaders into this short piece of code. It is self
contained and nearly minimal, apart from
-animating the Uniform variable for show effect
-shaders doing a little more than the necessary minimum (lighting,
animation, procedural texture)
-relying on osg::Box, osg::ShapeDrawable for geometry (some user
defined geometry with custom vertex attributes would be nice)
This code sample seems less confusing for GLSL newbies like myself,
when compared to the full osgshaders demo.
Next I will go shopping in the osgreflect demo, as suggested by Robert Osfield.
The goal would be to implement some reflecting and refracting object
as a single osg Node, which fits into any scene graph with minimal
fuss.
///////////////////////////////////////////////////////////////////////////
// in-line GLSL source code
static const char *blockyVertSource = {
"// blocky.vert - an GLSL vertex shader with animation\n"
"uniform float Sine;\n"
"const vec3 LightPosition = vec3(0.0, 0.0, 4.0);\n"
"const float BlockScale = 0.30;\n"
"// varyings are written by vert shader, interpolated, and read by
frag shader.\n"
"varying float LightIntensity;\n"
"varying vec2 BlockPosition;\n"
"void main(void)\n"
"{\n"
" // per-vertex diffuse lighting\n"
" vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;\n"
" vec3 tnorm = normalize(gl_NormalMatrix * gl_Normal);\n"
" vec3 lightVec = normalize(LightPosition - vec3 (ecPosition));\n"
" LightIntensity = max(dot(lightVec, tnorm), 0.0);\n"
" // blocks will be determined by fragment's position on the XZ plane.\n"
" BlockPosition = gl_Vertex.xz / BlockScale;\n"
" // scale the geometry based on an animation variable.\n"
" vec4 vertex = gl_Vertex;\n"
" vertex.w = 1.0 + 0.4 * (Sine + 1.0);\n"
" gl_Position = gl_ModelViewProjectionMatrix * vertex;\n"
"}\n"
};
static const char *blockyFragSource = {
"// blocky.frag - an GLSL fragment shader with animation\n"
"uniform float Sine;\n"
"const vec3 Color1 = vec3(1.0, 1.0, 1.0);\n"
"const vec3 Color2 = vec3(0.0, 0.0, 0.0);\n"
"// varyings are written by vert shader, interpolated, and read by
frag shader.\n"
"varying vec2 BlockPosition;\n"
"varying float LightIntensity;\n"
"void main(void)\n"
"{\n"
" vec3 color;\n"
" float ss, tt, w, h;\n"
" ss = BlockPosition.x;\n"
" tt = BlockPosition.y;\n"
" if (fract(tt * 0.5) > 0.5)\n"
" ss += 0.5;\n"
" ss = fract(ss);\n"
" tt = fract(tt);\n"
" // animate the proportion of block to mortar\n"
" float blockFract = (Sine + 1.1) * 0.4;\n"
" w = step(ss, blockFract);\n"
" h = step(tt, blockFract);\n"
" color = mix(Color2, Color1, w * h) * LightIntensity;\n"
" gl_FragColor = vec4 (color, 1.0);\n"
"}\n"
};
///////////////////////////////////////////////////////////////////////////
// callback for animating various Uniforms (currently only the SIN uniform)
class AnimateCallback: public osg::Uniform::Callback
{
public:
enum Operation { SIN };
AnimateCallback(Operation op) : _operation(op) {}
virtual void operator() ( osg::Uniform* uniform, osg::NodeVisitor* nv )
{
float angle = 2.0 * nv->getFrameStamp()->getSimulationTime();
float sine = sinf( angle ); // -1 -> 1
switch(_operation) {
case SIN : uniform->set( sine ); break;
}
}
private:
Operation _operation;
};
int main(int, char **)
{
// construct the viewer.
osgViewer::Viewer viewer;
// use a geode with a Box ShapeDrawable
osg::Geode* basicModel = new osg::Geode();
basicModel->addDrawable(new osg::ShapeDrawable(new
osg::Box(osg::Vec3(0.0f,0.0f,0.0f),1.0f)));
// create the "blocky" shader, a simple animation test
osg::StateSet *ss = basicModel->getOrCreateStateSet();
osg::Program* program = new osg::Program;
program->setName( "blocky" );
program->addShader( new osg::Shader( osg::Shader::VERTEX,
blockyVertSource ) );
program->addShader( new osg::Shader( osg::Shader::FRAGMENT,
blockyFragSource ) );
ss->setAttributeAndModes(program, osg::StateAttribute::ON);
// attach some animated Uniform variable to the state set
osg::Uniform* SineUniform = new osg::Uniform( "Sine", 0.0f );
ss->addUniform( SineUniform );
SineUniform->setUpdateCallback(new AnimateCallback(AnimateCallback::SIN));
// run the osg::Viewer using our model
viewer.setSceneData( basicModel );
return viewer.run();
}
/*EOF*/
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