Triangle Mesh: What's objective of graphics?- Given a 3D scene and a camera position, generate(render) a 2D image- What is the data structure/representation of 3Dscene?? For Simple primitives, such as sphere, cube..: Complex models, usually use triangle mesh orparameter curves/surfaces
Triangle Mesh • What’s objective of graphics? – Given a 3D scene and a camera position, generate (render) a 2D image. – What is the data structure/representation of 3D scene? • For Simple primitives, such as sphere, cube. • Complex models, usually use triangle mesh or parameter curves/surfaces
: Mesh Description: usually contains a list offaces F, and a list of vertices V A list of faces F = (fi,f2,...,fn): Each face is a triangle A list of vertices V = (Vi,V2,...,Vn)- Each face in F is a list of indices in Ve.g.fi --(V1, V2,V3 ), fz --(V4, Vs, V6)f3 --(V7,Vs,V9 ),
• Mesh Description: usually contains a list of faces F, and a list of vertices V – A list of faces F = (f1,f2,.,fn) • Each face is a triangle – A list of vertices V = (v1,v2,.,vn) – Each face in F is a list of indices in V e.g. f1 -(v1,v2,v3 ), f2 -(v4,v5,v6 ), f3 -(v7,v8,v9 ),
Some Samples: Examples of triangle mesh models, a bull, adragon and a head model. We drawtriangles over bull model, and show theother two models by shading
Some Samples • Examples of triangle mesh models, a bull, a dragon and a head model. We draw triangles over bull model, and show the other two models by shading
Normal· Face Normal- Each face has a normal direction to define the orientationVertex Normal- Each vertex is shared by m facesNormal- Compute normal by InterpolationNv= (Nf1+Nf2 ... + Nfm)/m- or by area based InterpolationNv=(IF1|*Nf1+|F2|*Nf2... +Fm|*Nfm)/(/F1|+|F2|+...JFmD
• Face Normal – Each face has a normal direction to define the orientation • Vertex Normal – Each vertex is shared by m faces – Compute normal by Interpolation Nv= (Nf1+Nf2 . + Nfm)/m – or by area based Interpolation Nv= (|F1|*Nf1+|F2|*Nf2 . + |Fm|*Nfm)/(|F1|+|F2|+.|Fm|) Normal Normal
Triangle Mesh: Rendering of mesh models- In each point of the mesh surface, we need tospecify a color: By Color: Given constant color to each face? By lighting- Suppose a light exists in the scene andilluminates the scene-How to calculate lighting?
Triangle Mesh • Rendering of mesh models – In each point of the mesh surface, we need to specify a color • By Color: Given constant color to each face • By lighting – Suppose a light exists in the scene and illuminates the scene. –How to calculate lighting?