From Christian Buchner, "The attached openscenegraph example is much simpler than

osgshaders.cpp and demonstrates the use of GLSL vertex and fragment
shaders with a simple animation callback. I found the osgshaders.cpp
too complex to serve as a starting point for GLSL programming"

examples/CMakeLists.txt

@@ -102,6 +102,7 @@ IF(DYNAMIC_OPENSCENEGRAPH)
     ADD_SUBDIRECTORY(osgshadow)
     ADD_SUBDIRECTORY(osgshape)
     ADD_SUBDIRECTORY(osgsharedarray)
+    ADD_SUBDIRECTORY(osgsimpleshaders)
     ADD_SUBDIRECTORY(osgsimplifier)
     ADD_SUBDIRECTORY(osgsimulation)
     ADD_SUBDIRECTORY(osgsidebyside)

examples/osgsimpleshaders/CMakeLists.txt

@@ -0,0 +1,3 @@
+SET(TARGET_SRC osgsimpleshaders.cpp )
+
+SETUP_EXAMPLE(osgsimpleshaders)

examples/osgsimpleshaders/osgsimpleshaders.cpp

@@ -0,0 +1,141 @@
+/* OpenSceneGraph example, osgminimalglsl.
+*
+*  Permission is hereby granted, free of charge, to any person obtaining a copy
+*  of this software and associated documentation files (the "Software"), to deal
+*  in the Software without restriction, including without limitation the rights
+*  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+*  copies of the Software, and to permit persons to whom the Software is
+*  furnished to do so, subject to the following conditions:
+*
+*  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+*  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+*  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+*  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+*  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+*  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+*  THE SOFTWARE.
+*/
+
+/* file:        examples/osgminimalglsl.cpp
+ *
+ * A minimal demo of the OpenGL Shading Language shaders using core OSG.
+ *
+ * blocky shader taken from osgshaders sample (Author: Mike Weiblein)
+*/
+
+#include <osgViewer/Viewer>
+
+#include <osg/ShapeDrawable>
+#include <osg/Geode>
+#include <osg/Vec3>
+
+#include <osg/Program>
+#include <osg/Shader>
+#include <osg/Uniform>
+
+using namespace osg;
+
+///////////////////////////////////////////////////////////////////////////
+// in-line GLSL source code
+
+static const char *blockyVertSource = {
+    "// blocky.vert - an GLSL vertex shader with animation\n"
+    "// the App updates uniforms \"slowly\" (eg once per frame) for 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"
+    "// the App updates uniforms \"slowly\" (eg once per frame) for 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*/