 Engineering Graphics & Introductory Design 3D Graphics and Rendering REU Modeling Course – June 13 th 2014

Purpose of 3D Graphics  3D computer graphics is the science, study, and method of projecting a mathematical representation of 3D objects onto a 2D display  Viewpoints (e.g. perspective)  Lighting and shading  Texturing

Purposes  Visualization – generate representations of objects  Engineering – CAD, Analysis, Working drawings  Photorealistic rendering – produce computer generated images that look like reality  Much more complicated and time-consuming to do

Real or Not??

CAD and Engineering Viz  Equations to represent 3D objects  Requires substantial computing resources  Difficult for real-time simulations and computer games

Polygonal Models  Modeling objects by sampling only certain points (vertices) on the object  Connect using linear segments  More computationally efficient (try to maintain low-poly models)

Photorealistic Rendering  Need specific techniques for:  Lighting  Shading  Texturing  Bump mapping, etc.  To mimic physical effects and produce a realistic image

Texture Mapping  Also called “texturing” – a process of wrapping a flat texture (2D image) onto curved 3D geometry

Lighting & Shading  Rendering programs allow fine control over lights  Sources (e.g. ambient, spot, omnidirectional)  Color, Intensity

Lighting & Shading  Lighting calculations are performed to determine reflectivity of objects (e.g. “shininess” or “dullness”)  Also where light does/doesn’t hit - shadows

Bump Mapping  Bump maps simulate the roughness of surfaces even though the computer surfaces are generally flat  Higher areas are light and lower areas are dark  Create grayscale image to achieve this effect

3D Rendering  Pixel-oriented rendering – Ray tracers  Operates by tracing light rays as they intersect objects in the scene and the projection plane  Very computationally expensive  Polygon-oriented rendering – Scan-line renderers  Operate object to object. Each polygon is drawn to screen.  All objects are tessellated into polygons and then pixels

3D Rendering – Ray Tracing  Does not take into account inter-reflections of diffuse light, resulting in hard shadows – add Radiosity

Scan-Line Rendering  Lighting and shading is calculated using the normal vector of each polygon  Linearly interpolated color across the polygon  Shading methods  Flat  Gourand  Phong

Scan-Line Rendering - Shading  Phong is most realistic, but takes much more computation

Final  A lot of other techniques to optimize as well as improve visual quality  Clipping planes  Real-time raycasting  Image compression  …

Advanced Tutorials  Bump mapping using Photoshop   Adding a light scene in Maya using a background image   Creating hair on a character in Maya 

Try it out  Create a scene in Maya  Add a texture map, you can download images from Google  Experiment with bump mapping o Open your texture map in Photoshop and follow instructions on the tutorial o Notice the changes that occur when adjusting the bump depth  Add light sources (area, spot, ambient, directional) o You can adjust the intensity and position as well as turning on shadows to develop your desired scene