lecture04-1

Origin looking down z axis up vector aligned with y

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Unformatted text preview: era’s vertical up[XYZ]: vector Creates a matrix that transforms points in world coordinates to camera coordinates Creates camera • Camera at origin • Looking down -Z axis • Up vector aligned with Y axis OpenGL: Perspective Projection In OpenGL: In • Projections implemented by projection matrix Projections projection • gluPerspective() creates a perspective projection matrix: projection glSetMatrix(GL_PROJECTION); glLoadIdentity(); //load an identity matrix gluPerspective(vfov, aspect, near, far); Parameters to gluPerspective(): Parameters gluPerspective() • vfov: vertical field of view • aspect: window width/height • near, far: distance to near & far clipping planes far OpenGL: Lighting Setup lighting, if any Simplest option: change the current color between Simplest current polygons or vertices polygons • glColor() sets the current color Or OpenGL provides a simple lighting model: • Set parameters for light(s) – Intensity, position, direction & falloff (if applicable) Intensity, • Set material parameters to describe how light reflects from the Set material surface surface Won’t go into details now; check the red book if Won’t interested interested OpenGL: Specifying Geometry Geometry in OpenGL consists of a list of vertices in Geometry between calls to glBegin() and glEnd() glBegin() glEnd() • A simple example: telling GL to render a triangle glBegin(GL_POLYGON); glVertex3f(x1, y1, z1); glVertex3f(x2, y2, z2); glVertex3f(x3, y3, z3); glEnd(); • Usage: glBegin(geomtype) where geomtype is: Usage: glBegin( – Points, lines, polygons, triangles, quadrilaterals, etc... Primitive Types GL_POINTS GL_LINE • {S | _STRIP | _LOOP} GL_TRIANGLE • {S | _STRIP | _FAN} GL_QUAD • {S | _STRIP} GL_POLYGON GL_POLYGON List of vertices defines polygon edges Polygon must be convex Non-planar Polygons Imagine polygon with non-planar vertices Some perspectives will be rendered as concave Some polygons polygons These concave polygons may not rasterize These correctly correctly OpenGL: More Examples Example: GL supports quadrilaterals: glBegin(GL_QUADS); glVertex3f(-1, 1, 0); glVertex3f(-1, glVertex3f(-1, -1, 0); glVertex3f(-1, glVertex3f(1, -1, 0); glVertex3f(1, 1, 0); glEnd(); • This type of operation is called immediate-mode rendering; This immediate-mode each command h...
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