glPolygonMode example c c++ java objc

Name

glPolygonMode — select a polygon rasterization mode

C Specification

`void glPolygonMode(`	GLenum	`face`,
	GLenum	`mode)`;

Parameters

face: Specifies the polygons that mode applies to. Must be GL_FRONT for front-facing polygons, GL_BACK for back-facing polygons, or GL_FRONT_AND_BACK for front- and back-facing polygons.
mode: Specifies how polygons will be rasterized. Accepted values are GL_POINT, GL_LINE, and GL_FILL. The initial value is GL_FILL for both front- and back-facing polygons.

Description

glPolygonMode controls the interpretation of polygons for rasterization. face describes which polygons mode applies to: front-facing polygons (GL_FRONT), back-facing polygons (GL_BACK), or both (GL_FRONT_AND_BACK). The polygon mode affects only the final rasterization of polygons. In particular, a polygon's vertices are lit and the polygon is clipped and possibly culled before these modes are applied.
Three modes are defined and can be specified in mode: (glPolygonMode)

GL_POINT: Polygon vertices that are marked as the start of a boundary edge are drawn as points. Point attributes such as GL_POINT_SIZE and GL_POINT_SMOOTH control the rasterization of the points. Polygon rasterization attributes other than GL_POLYGON_MODE have no effect.
GL_LINE: Boundary edges of the polygon are drawn as line segments. They are treated as connected line segments for line stippling; the line stipple counter and pattern are not reset between segments (see glLineStipple). Line attributes such as GL_LINE_WIDTH andGL_LINE_SMOOTH control the rasterization of the lines. Polygon rasterization attributes other than GL_POLYGON_MODE have no effect.
GL_FILL: The interior of the polygon is filled. Polygon attributes such as GL_POLYGON_STIPPLE and GL_POLYGON_SMOOTH control the rasterization of the polygon.

Examples

To draw a surface with filled back-facing polygons and outlined front-facing polygons, call

glPolygonMode(GL_FRONT, GL_LINE);

Notes

Vertices are marked as boundary or nonboundary with an edge flag. Edge flags are generated internally by the GL when it decomposes polygons; they can be set explicitly using glEdgeFlag.

Errors

GL_INVALID_ENUM is generated if either face or mode is not an accepted value.
GL_INVALID_OPERATION is generated if glPolygonMode is executed between the execution of glBegin and the corresponding execution of glEnd.

Associated Gets

glGet with argument GL_POLYGON_MODE

Copyright

Example of glPolygonMode

void RenderScene(void)
{
        GLfloat x,y,angle;
        int iPivot = 1;
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        if(bCull)
                glEnable(GL_CULL_FACE);
        else
                glDisable(GL_CULL_FACE);

        if(bDepth)
                glEnable(GL_DEPTH_TEST);
        else
                glDisable(GL_DEPTH_TEST);

        if(bOutline)
                glPolygonMode(GL_BACK,GL_LINE);
        else
                glPolygonMode(GL_BACK,GL_FILL);

        glPushMatrix();
        glRotatef(xRot,1.0f,0.0f,0.0f);
        glRotatef(yRot,0.0f,1.0f,0.0f);
        glBegin(GL_TRIANGLE_FAN);
        glVertex3f(0.0f,0.0f,75.0f);
        for(angle=0.0f; angle < (2.0f*GL_PI); angle +=(GL_PI/8.0f))
        {
                x = 50.0f*sin(angle);
                y = 50.0f*cos(angle);
                if((iPivot %2) == 0)
                        glColor3f(0.0f,1.0f,0.0f);
                else
                        glColor3f(1.0f,0.0f,0.0f);

                iPivot++;
                glVertex2f(x,y);
        }
        glEnd();
        glBegin(GL_TRIANGLE_FAN);
        glVertex2f(0.0f,0.0f);
        for(angle = 0.0f; angle < (2.0f*GL_PI); angle += (GL_PI/8.0f))
        {
                x=50.0f*sin(angle);
                y=50.0f*cos(angle);

                if((iPivot %2) == 0)
                        glColor3f(0.0f,1.0f,0.0f);
                else
                        glColor3f(1.0f,0.0f,0.0f);
                iPivot++;
                glVertex2f(x,y);
        }
        glEnd();
        glPopMatrix();
        glFlush(); }

Example source code bank

Thursday, June 2, 2011