swrast: drawing a line 2.0px in width has incorrect offset

Submitted by Campbell Barton

Assigned to mes..@..op.org

Link to original bug (#11956)

Description

Hi, when using blender3d with Mesa's libGL.so I notice a display problem that isnt present with NVidia's or ATI's drivers.

http://members.optusnet.com.au/cjbarton/mesabug.png

This looks to be a bug in Mesa's line drawing function since blender uses it to draw the outline.

Note that mesa has done this for a long time, and older versions had this problem also.

The example below uses glLineWidth(2.0) and glDepthMask(0) and I assume line drawing with glLineWidth(2.0) to be the problem.

is the function in blender that draws the outline around the mesh - drawobject.c:1938

/* Mesh drawing routines */

static void draw_mesh_object_outline(Object *ob, DerivedMesh *dm) {

if(G.vd->transp==0) {	// not when we draw the transparent pass
	glLineWidth(2.0);
	glDepthMask(0);
	
	/* if transparent, we cannot draw the edges for solid select... edges have no material info.
	   drawFacesSolid() doesn't draw the transparent faces */
	if(ob->dtx & OB_DRAWTRANSP) {
		glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); 
		dm->drawFacesSolid(dm, set_gl_material);
		glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
	}
	else {
		dm->drawEdges(dm, 0);
	}
				
	glLineWidth(1.0);
	glDepthMask(1);
}

}