Draw selection rectangle via screen shader

Author: ruberith

GUI/OpenGL/MiniGL.cpp

@@ -70,6 +70,7 @@ GLFWwindow* MiniGL::m_glfw_window = nullptr;
 bool MiniGL::m_vsync = false;
 double MiniGL::m_lastTime;
 Shader MiniGL::m_shader;
+Shader MiniGL::m_shader_screen;
 Matrix4r MiniGL::m_modelview_matrix;
 Matrix4r MiniGL::m_projection_matrix;
 Vector3r MiniGL::m_ambientIntensity;
@@ -117,11 +118,9 @@ void MiniGL::coordinateSystem()
 
 void MiniGL::drawVector(const Vector3r &a, const Vector3r &b, const float w, float *color)
 {
-	float thickness = 0.001 * w;
+	float thickness = 0.001f * w;
 
-	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
 	drawCylinder(a, b, color, thickness, 8, false);
-	glPolygonMode(GL_FRONT_AND_BACK, drawMode);
 }
 
 void MiniGL::drawCylinder(const Vector3r &a, const Vector3r &b, const float *color, const float radius, const unsigned int subdivisions, const bool lighting)
@@ -710,7 +709,7 @@ void MiniGL::initLights ()
 	m_lightPosition.segment<3>(2 * 3) << 0.0, 10.0, 10.0;
 }
 
-void MiniGL::initShader(const std::string& shaderPath)
+void MiniGL::initShaders(const std::string& shaderPath)
 {
 	Shader& shader = m_shader;
 	shader.compileShaderFile(GL_VERTEX_SHADER, shaderPath + "/mini.vert");
@@ -730,6 +729,16 @@ void MiniGL::initShader(const std::string& shaderPath)
 	shader.addUniform("specularReflectance");
 	shader.addUniform("shininess");
 	shader.end();
+
+    Shader& screenShader = m_shader_screen;
+    screenShader.compileShaderFile(GL_VERTEX_SHADER, shaderPath + "/mini_screen.vert");
+    screenShader.compileShaderFile(GL_FRAGMENT_SHADER, shaderPath + "/mini_screen.frag");
+    screenShader.createAndLinkProgram();
+    screenShader.begin();
+    screenShader.addUniform("width");
+    screenShader.addUniform("height");
+    screenShader.addUniform("color");
+    screenShader.end();
 }
 
 void MiniGL::enableShader(const Vector3r& ambientReflectance, const Vector3r& diffuseReflectance, const Vector3r& specularReflectance, const Real shininess, const Real pointSize)
@@ -759,6 +768,21 @@ void MiniGL::disableShader()
 	shader.end();
 }
 
+void MiniGL::enableScreenShader(const Vector3r& color)
+{
+    Shader& shader = m_shader_screen;
+    shader.begin();
+    glUniform1f(shader.getUniform("width"), static_cast<Real>(m_width));
+    glUniform1f(shader.getUniform("height"), static_cast<Real>(m_height));
+    glUniform3fv(shader.getUniform("color"), 1, &color(0));
+}
+
+void MiniGL::disableScreenShader()
+{
+    Shader& shader = m_shader_screen;
+    shader.end();
+}
+
 void MiniGL::supplyVectors(GLuint index, GLuint vbo, unsigned int dim, unsigned int n, const Real* data)
 {
 	glBindBuffer(GL_ARRAY_BUFFER, vbo);
@@ -1006,25 +1030,17 @@ void MiniGL::error_callback(int error, const char* description)
 
 void MiniGL::drawSelectionRect()
 {
-	glDisable(GL_LIGHTING);
-	glPushMatrix();
-	glLoadIdentity();
-	glMatrixMode(GL_PROJECTION);
-	glPushMatrix();
-	glLoadIdentity();
-	glOrtho(0.0f, m_width, m_height, 0.0f, -1.0f, 1.0f);
-	glBegin(GL_LINE_LOOP);
-	glColor3f(1, 0, 0); //Set the colour to red
-	glVertex2f(static_cast<GLfloat>(m_selectionStart[0]), static_cast<GLfloat>(m_selectionStart[1]));
-	glVertex2f(static_cast<GLfloat>(m_selectionStart[0]), static_cast<GLfloat>(mouse_pos_y_old));
-	glVertex2f(mouse_pos_x_old, mouse_pos_y_old);
-	glVertex2f(mouse_pos_x_old, m_selectionStart[1]);
-	glEnd();
-	glPopMatrix();
-	glMatrixMode(GL_MODELVIEW);
-
-	glPopMatrix();
-	glEnable(GL_LIGHTING);
+    Real selectionRect[] = {
+            static_cast<Real>(m_selectionStart[0]), static_cast<Real>(m_selectionStart[1]),
+            static_cast<Real>(m_selectionStart[0]), static_cast<Real>(mouse_pos_y_old),
+            static_cast<Real>(mouse_pos_x_old), static_cast<Real>(mouse_pos_y_old),
+            static_cast<Real>(mouse_pos_x_old), static_cast<Real>(m_selectionStart[1])
+    };
+    enableScreenShader(Vector3r(1, 0, 0));
+    supplyVectors(0, m_vbo_vertices, 2, 4, &selectionRect[0]);
+    glDrawArrays(GL_LINE_LOOP, 0, 4);
+    glDisableVertexAttribArray(0);
+    disableScreenShader();
 }
 
 void MiniGL::mainLoop()

GUI/OpenGL/MiniGL.h

@@ -109,6 +109,7 @@ namespace SPH
 		static bool m_vsync;
 		static double m_lastTime;
 		static Shader m_shader;
+        static Shader m_shader_screen;
 		static Matrix4r m_modelview_matrix;
 		static Matrix4r m_projection_matrix;
 		static Vector3r m_ambientIntensity;
@@ -220,9 +221,11 @@ namespace SPH
 		static const Matrix4r& getModelviewMatrix() { return m_modelview_matrix; }
 		static const Matrix4r& getProjectionMatrix() { return m_projection_matrix; }
 
-		static void initShader(const std::string& shaderPath);
+		static void initShaders(const std::string& shaderPath);
 		static void enableShader(const Vector3r& ambientReflectance, const Vector3r& diffuseReflectance, const Vector3r& specularReflectance, const Real shininess, const Real pointSize=1.0);
 		static void disableShader();
+        static void enableScreenShader(const Vector3r& color);
+        static void disableScreenShader();
 
 		static const GLuint getVao() { return m_vao; }
 		static const GLuint getVboVertices() { return m_vbo_vertices; }

Simulator/GUI/OpenGL/Simulator_OpenGL.cpp

@@ -33,7 +33,7 @@ Simulator_OpenGL::~Simulator_OpenGL(void)
 
 void Simulator_OpenGL::initShaders(const std::string &shaderPath)
 {
-	MiniGL::initShader(shaderPath);
+	MiniGL::initShaders(shaderPath);
 
 	string vertFile = shaderPath + "/vs_points_vector.glsl";
 	string fragFile = shaderPath + "/fs_points.glsl";

Tools/PartioViewer/GUI/OpenGL/PartioViewer_OpenGL.cpp

@@ -55,7 +55,7 @@ void PartioViewer_OpenGL::getImage(int width, int height, unsigned char *image)
 
 void PartioViewer_OpenGL::initShaders(const std::string &shaderPath)
 {
-	MiniGL::initShader(shaderPath);
+	MiniGL::initShaders(shaderPath);
 
 	string vertFile = shaderPath + "/vs_points_vector.glsl";
 	string fragFile = shaderPath + "/fs_points.glsl";

data/shaders/mini_screen.frag

@@ -0,0 +1,10 @@
+#version 330
+
+uniform vec3 color;
+
+out vec4 outColor;
+
+void main()
+{
+    outColor = vec4(color, 1.0);
+}

data/shaders/mini_screen.vert

@@ -0,0 +1,11 @@
+#version 330
+
+uniform float width;
+uniform float height;
+
+layout(location = 0) in vec2 position;
+
+void main()
+{
+    gl_Position = vec4(2.0 * (position.x / width) - 1.0, -2.0 * (position.y / height) + 1.0, -1.0, 1.0);
+}