Unformatted text preview:

CSC 220 3D Computer Graphics Fall 2003Graphics HardwareColor for Computer GraphicsGraphics SoftwareGraphics File FormatsThe Graphics PipelineModeling TechniquesSlide 8Teddy – a Modeling AppletTERASome Visual CuesSurface AlgorithmsSome Minimal MathematicsThe Z-buffer MethodPOV-RaySpecifying an Image in SDLSimple ShapesConstructive Solid GeometryTransformation of CoordinatesZ-Buffer ShadingLights in POV-RayReflected LightRay Tracer Shading2D Texture Mapping3D Texture MappingViewing – the Synthetic CameraLight and its PerceptionThe Human EyeThe Color CubesThe HSV Color SystemHalftoningSome Advanced ShapesNURBSThe Rhino InterfaceViewing in RhinoDrawing LinesModeling AidsEditing ObjectsRhino GeometryCreating CurvesCreating SurfacesCreating SolidsTechnical Side of AnimationArtistic Side of AnimationCSC 220 3D Computer Graphics Fall 2003Graphics HardwareText Mode – Characters (2K bytes)Graphics Modes – Pixels (millions of bytes) x-y coordinate systemRaster Scan with Frame Buffer (aliasing)Vector Scan with Display ListColor for Computer GraphicsRed, Green, Blue phosphors and shadow maskVGA – 640 x 480 with 16 colorsVGA – 320 x 200 with 256 colors, using the Color LookUp Table (CLUT) – 8 bits / pixel is 256 colors at one time, but 262,144 colors in paletteSVGA with True Color – 800 x 600 (or more), using 24 bits / pixel – millions of colors simultaneouslyGraphics SoftwareBASIC is an exceptionAPI’s, or librariesBorland Graphical Interface (BGI)Graphical Kernel System (GKS)OpenGL …Graphics File FormatsGIFJPEGBMPTIFFTarga…The Graphics PipelineModeling – geometry of an objectViewing – how the object appearshidden surfacessynthetic cameraRendering – realism and morelightingshadingtexturesshadowsModeling TechniquesPolygons (Triangles)Splines (NURBS)Constructive Solid Geometry (CSG)Fractals …Teddy – a Modeling AppletSimple and quickFor rough models instantlySpherical topologyOperationscreationextrusioncuttingbendingTERAA tool for visual literacyCan display 500,000 combinations of images rendered by various methodsCan be used in two waysexplore rendering effectsself-test rendering effectsContains POV-Ray files alsoSome Visual CuesVisibilityShadowsReflectionsRefractionSurface AlgorithmsVisibilitywireframe – ambiguityhidden lines / surfacesRendering techniques (2 of many)z-bufferray tracingSome Minimal Mathematics3D coordinates – x,y,z as LHSVectors – direction and magnitudeNormal vector to a surfaceCulling back facesThe Z-buffer MethodAlong with frame buffer have a z-buffer:Frame buffer holds color value for the pixelZ-buffer holds z value for the pixel location Scan each surface in succession. If z value for this location on this surface is less than value in z-buffer, replace color in frame buffer and update value in z-bufferMost common rendering method, often with special hardwarePOV-Ray No modeling, uses Scene Description Language (SDL)Does viewing and renderingNo books in print, but excellent on-line documentationExercises from TERA textrender gold.pov, p.9render room.pov, p.20revise camera orientation of room, pp.21,22Specifying an Image in SDLObjectsSimple shapesCSG objectsAdvanced shapesTransformationsTextureCameraLightingSimple ShapesSpheresBoxesConesCylindersPlanesConstructive Solid GeometryUnionIntersectionDifferenceMergeTransformation of CoordinatesAffine transformations translation scaling rotationComposition of affine transformationsProperties of affine transformationsstraight lines stay straightparallel lines stay parallelangles do NOT stay fixed, except for rigid transformations (no scaling)Z-Buffer ShadingConstant Shading – color computed once for entire objectFaceted Shading – color computed once for each polygonGouraud Shading – color computed using vertex normal, then double interpolation of color values in the polygonPhong Shading – double interpolation of vertex normals, then color value computed for each interpolated vector value in the polygonLights in POV-RayPoint lightsSpotlightsradiusfallofftightnessadaptivejitterCylinder lights (same parameters as spotlight)Area lightsAmbient lightingReflected LightWhen light strikes a surface, some colors are absorbed, and we see the colors that are reflected.We deal with three types of reflections:ambient reflected lightdiffuse reflected lightspecular reflected light (Phong illumination) Computing the reflected values requires that vectors must be multiplied.Ray Tracer ShadingMultiple reflectionsTransparencyRefractionShadows2D Texture MappingMap Types planar – normal parallel to X, Y, or Z cylindrical – rotation around X, Y, or Z spherical – rotation around X, Y, or Z box – normal parallel to X, Y, or ZProblems poles distortion aliasingBilateral symmetry and planar maps3D Texture MappingProcedural – texture is function f(x,y,z)Common textures are stripes, rings, rampsNoise for realistic effects amplitude frequency use of higher order terms eccentricity, tilt, and twistTexture functions in POV-Ray for glass, metal, stone, and woodViewing – the Synthetic CameraWorld Coordinates (WC) – x,y,zr is location of camera in WCThe View Plane – U,V,NN is where camera is lookingV is up direction, orthogonal to NU is 3rd axis, orthogonal to both N and VLight and its PerceptionIn describing the effects of light we must take into account both physics and physiology.The wavelength of visible light varies from 400 nanometers (violet) to 700 nanometers (red).In describing the quality of light, we need three parameters: hue – the dominant wavelength intensity (physics) or brightness (physiology) saturation – the purity of the hueThe Human EyeThe eye has rods that are very sensitive to light versus dark (about 1 photon), and cones that are less sensitive to level (about 5 photons) but can distinguish colors.There are cones sensitive to blue, to green, and to red. They are all in the fovea (1/4 mm), and are the basis of the tristimulus theory of vision. Light which is a mixture of red and green looks just as yellow as does pure yellow light! The human visual system cannot detect overtones and harmonics as does the human auditory system.The Color


View Full Document

UNCW CSC 220 - CSC 220 3D Computer Graphics

Download CSC 220 3D Computer Graphics
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view CSC 220 3D Computer Graphics and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view CSC 220 3D Computer Graphics 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?