Hi guys, i’m a beginner with OpenGL…
i’m trying to draw a translucent rectangle on my terrain, but the rectangle keeps flickering on one of triangle.
I have tried to render it as a triangle strip, but the problem still persist…
could some one please give me some pointers on how should i resolve the issue?
following is the code that i wrote to render the rectangle…
glDisable(GL_TEXTURE_2D);
glDisable(GL_LIGHTING);
glDisable(GL_DEPTH_TEST);
glDepthMask(GL_FALSE);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBegin(GL_TRIANGLE_STRIP);
glColor4f(glowR, glowG, 0.0f, glowTransparency);
glVertex3d(MAP_SIZE_X, 0, 0);
glColor4f(glowR, glowG, 0.0f, glowTransparency);
glVertex3d(0, 0, 0);
glColor4f(glow2R, glow2G, 0.0f, glowTransparency);
glVertex3d(MAP_SIZE_X, 0, MAP_SIZE_Z);
glColor4f(glow2R, glow2G, 0.0f, glowTransparency);
glVertex3d(0, 0, MAP_SIZE_Z);
glEnd();
glDepthMask(GL_TRUE);
glEnable(GL_DEPTH_TEST);
glEnable(GL_TEXTURE_2D);
glEnable(GL_LIGHTING);
this is the main file, with the projection matrices, viewport and stuff…
/**
* Render the scene
*/
void RenderScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
//set projection matrix and view volume
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho (0,1024,0,768, -100, 0);
glMultMatrixd(proj_homograph);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity(); //Reset modelview matrix for new frame.
if(isCalibrationStarted())
{
//calibrate the system
calibrateSystem();
}
else
{
glRotatef(Rotate, 0, 0, 1);
if(locateShape)
{
generateTerrain();
}
else
{
drawSun();
renderCalibration();
}
renderTerrain();
//Draw translucent objects last
if(!locateShape)
{
if(showTerrain)
{
renderWater();
renderEruption();
drawDawn();
}
else if(isWaterShown())
{
renderWater();
}
}
}//end of else
glFlush();
glutSwapBuffers();
}
//****************************** idle function *******************************
static void idle( void )
{
glutPostRedisplay();
}
//***************************** reshape function *******************************
static void reshape( int width, int height )
{
glViewport(0, 0, (GLint)width, (GLint)height);
}
void initialiseGraphics()
{
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowPosition(0,0);
glutInitWindowSize(1024,768);
projNo = glutCreateWindow("Sandbox Alive!");
glutFullScreen();
glutDisplayFunc(RenderScene);
glutIdleFunc( idle );
glutReshapeFunc( reshape );
ShowCursor(false);
//glutSetWindow(projNo);
glShadeModel(GL_SMOOTH); // Enable Smooth Shading
glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black Background
glClearDepth(1.0f); // Depth Buffer Setup
glEnable(GL_DEPTH_TEST); // Enables Depth Testing
glDepthFunc(GL_LEQUAL); // The Type Of Depth Testing To Do
glEnable(GL_CULL_FACE); // Enable Culling
glFrontFace(GL_CCW); // Draw CCW front-facing polygons only
glEnable(GL_POLYGON_SMOOTH); // Antialiasing Polygons
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}
void initialise()
{
initialiseGraphics();
initialiseUI();
initialiseLight();
initialiseWater();
initialiseTerrain();
initialiseCloud();
initialiseValues();
initialiseVolcanoEngine();
//initialise projector homograph
Matrix temp = proj_computeHomograph(point3D, proj_point2D, 6);
temp = cam_computeHomograph(point3D, cam_point2D, 6);
initialiseCam();
previewCam();
cout << "done init" << endl;
}
//************************** Main Function *******************************
int main(int argc, char* argv[])
{
totalHorX = (abs(MAP_SIZE_X/stripeWidth) - rowIndex + 1)/incrementStep + 1;
totalVerZ = (abs(MAP_SIZE_Z/stripeWidth) - colIndex + 1)/incrementStep + 1;
glutInit(&argc, argv);
initialise();
glutMainLoop();
return 0;
}
