8 add graphics operation to enable vertex aliasing

src/CMakeLists.txt

@@ -1,19 +1,14 @@
-add_library(
-  osgTools STATIC osgTools/StatsHandler.cpp include/osgTools/StatsHandler.h
-                  include/osgTools/Version.h)
+set(PUBLIC_HEADERS
+    include/osgTools/GraphicsOperations.h include/osgTools/PointShaderProgram.h
+    include/osgTools/StatsHandler.h include/osgTools/Version.h)
+add_library(osgTools STATIC osgTools/PointShaderProgram.cpp
+                            osgTools/StatsHandler.cpp "${PUBLIC_HEADERS}")
 
 add_library(osgTools::osgTools ALIAS osgTools)
 
 target_link_libraries(osgTools PUBLIC ${OPENSCENEGRAPH_LIBRARIES})
-target_sources(
-  osgTools
-  PUBLIC FILE_SET
-         HEADERS
-         BASE_DIRS
-         include
-         FILES
-         include/osgTools/StatsHandler.h
-         include/osgTools/Version.h)
+target_sources(osgTools PUBLIC FILE_SET HEADERS BASE_DIRS include FILES
+                               "${PUBLIC_HEADERS}")
 
 install(
   TARGETS osgTools

src/include/osgTools/GraphicsOperations.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <osg/GraphicsContext>
+
+namespace osgTools {
+    //
+    // Graphics Operations
+    //
+
+    // UseVertexAttributeAliasing
+    //
+    // Enable with:
+    //      viewer.setRealizeOperation(new UseVertexAttributeAliasing());
+    //
+    class UseVertexAttributeAliasing : public osg::GraphicsOperation {
+    public:
+        UseVertexAttributeAliasing()
+            : osg::Referenced(true),
+              osg::GraphicsOperation("GraphicsOperation", false) {}
+
+        virtual void operator()(osg::GraphicsContext* gc) {
+            gc->getState()->setUseVertexAttributeAliasing(true);
+        }
+    };
+}  // namespace osgTools

src/include/osgTools/PointShaderProgram.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <osg/Node>
+#include <osg/Program>
+
+namespace osgTools {
+    osg::ref_ptr<osg::Program> createPointShaderProgram(osg::Node *targetNode);
+};

src/osgTools/PointShaderProgram.cpp

@@ -0,0 +1,60 @@
+#include <osgTools/PointShaderProgram.h>
+
+using namespace osgTools;
+
+const char* vertexShaderSource = R"(
+    #version 330 core
+
+    in vec4 osg_Vertex;
+    in vec4 osg_Color;
+
+    uniform mat4 osg_ModelViewProjectionMatrix;
+
+    out vec4 vertexColor;
+
+    void main(void) {
+        gl_Position = osg_ModelViewProjectionMatrix * osg_Vertex;
+
+        vertexColor = osg_Color;
+
+        // Be sure and call `StateSet::setMode(GL_PROGRAM_POINT_SIZE, osg::StateAttribute::ON)`, or
+        // this will be a no-op! IMPORTANT!
+        gl_PointSize = 1.0;
+    }
+)";
+
+const char* fragmentShaderSource = R"(
+    #version 330 core
+    in vec4 vertexColor;
+
+    out vec4 color;
+
+    void main(void) {
+        // Convert to [-1, 1] so (0,0) is the center of the point.
+        vec2 p = gl_PointCoord * 2.0 - 1.0;
+
+        // This gives us a radial coordinate without a costly sqrt(), supposedly.
+        float r2 = dot(p, p);
+
+        // This explicitly recreates legacy FFP point behavior...
+        float alpha = exp(-r2 * 2.5);
+        color = vec4(vertexColor.rgb * alpha, vertexColor.a   * alpha);
+    }
+)";
+
+osg::ref_ptr<osg::Program> osgTools::createPointShaderProgram(
+    osg::Node* target) {
+    osg::ref_ptr<osg::Program> prg = new osg::Program();
+
+    prg->addShader(new osg::Shader(osg::Shader::VERTEX, vertexShaderSource));
+    prg->addShader(
+        new osg::Shader(osg::Shader::FRAGMENT, fragmentShaderSource));
+
+    if (target) {
+        auto stateSet = target->getOrCreateStateSet();
+        stateSet->setAttributeAndModes(prg);
+        stateSet->setMode(GL_PROGRAM_POINT_SIZE, osg::StateAttribute::ON);
+    }
+
+    return prg;
+}