CODEWITHSUNDEEP
iphoneopengl-es
Alexey
Alexey

Reputation: 505

Strange black pixels on model

I tried to draw a model with 197 polygons but i have strange black pixels on it:

alt text http://i.imagehost.org/0398/IMG_0172.png

When I run the code in the iPhone Simulator, it shows well without those black pixels, but on the device I have that problem.

I set perspective:

const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0; 
GLfloat size; 
glEnable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION); 
size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0); 

CGRect rect = self.bounds; 
glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar); 
glViewport(0, 0, rect.size.width, rect.size.height);  
glMatrixMode(GL_MODELVIEW);

glLoadIdentity(); 
glClearColor(0.3f, 0.3f, 0.3f, 1.0f); 
glColor4f(0,0,0,0.5f);
glEnable(GL_SMOOTH);

glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);

glEnableClientState(GL_VERTEX_ARRAY);

And draw (model vertices, indexes and normals store in global arrays.):

glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

[EAGLContext setCurrentContext:context];

glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);


glTranslatef(1.0, -9, -22);

glVertexPointer(3, GL_FLOAT, 0, vertices);

glEnableClientState(GL_NORMAL_ARRAY);
glNormalPointer(GL_FLOAT, 0, normals);

glDrawElements(GL_TRIANGLES, 3*192, GL_UNSIGNED_BYTE, icosahedronFaces);

glDisableClientState(GL_NORMAL_ARRAY);

glTranslatef(-1.0, 9, 22);

glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER_OES];

Upvotes: 1

Views: 155

Answers (2)

prideout
prideout

Reputation: 3019

This could be a depth precision issue where the back-facing polygons are poking through. Try increasing the value of zNear as much as possible without clipping your scene.

Upvotes: 2

Soviut
Soviut

Reputation: 91545

It looks like an issue with some of the normals not being exactly perpendicular to their respective surface.

Try applying your normals before you translate.

Upvotes: 0

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