Stretch tasks How 3D models are built

Round 1: Quiz Blitz

1. 8 One at each corner: 4 on the top and 4 on the bottom.
2. 12 4 round the top, 4 round the bottom and 4 joining them.
3. The complete set of vertices, edges and faces of an object The mesh is the whole wireframe shape of the model.
4. True With enough tiny triangles, the edges become invisible and the surface looks smooth.
5. A game must draw about 60 frames every second A film can spend hours on each frame. A game has a sixtieth of a second.
6. More detail and smoother curves; More processing power and memory are needed This is the central trade off of 3D work: detail against performance.
7. Extrude Extruding a face of a cube upwards is how a box becomes, say, a chimney.
8. A mirror modifier Mirror is a non-destructive modifier: change one side and the other follows.
9. Vertex → Edge → Face → Mesh Points join to make edges, edges enclose faces, and faces together make a mesh.
10. 12 6 x 2 = 12. Games usually break every face down into triangles like this.
11. Its position in 3D space Three axes, three numbers: across, depth and height.
12. 9 3 on each triangle end and 3 joining the ends. For any simple solid, vertices - edges + faces = 2: 6 - 9 + 5 = 2.

Round 2: Quick Fire

1. • A vertex is a single point in 3D space
   • An edge is a straight line joining two vertices
   • A face is a flat surface enclosed by edges
   Model answer

   A vertex is a single point in 3D space with x, y and z coordinates. An edge is a straight line joining two vertices. A face is a flat surface enclosed by edges, usually a triangle or a square.

2. • More polygons give more detail and smoother curves
   • But they need more processing power and memory
   Model answer

   More polygons give more detail and smoother curves, but they need more processing power and memory, so the model is slower to display.

3. • Each film frame is rendered once, in advance, and can take hours
   • A game must draw about 60 frames every second, in real time
   Model answer

   Each frame of a film is rendered once, in advance, and can take hours. A game has to draw about 60 frames every second, in real time, while responding to the player, so its models must be far simpler.

4. • Extrude: pull a face outwards to make new geometry
   • Subdivide: split faces into smaller ones to add detail
   • Loop cut: add a ring of new edges around a model
   • Mirror modifier: build one half and reflect it
   • Primitives: start from a basic shape such as a cube
   Model answer

   Extrude pulls a face outwards to create new geometry. Subdivide splits faces into smaller ones to add detail.

Round 3: Big Think

1. • Start from a cube
   • Scale it flat to make the seat
   • Extrude faces downwards to make the legs
   • Extrude upwards to make the back
   • Add detail with loop cuts or subdividing, or use mirror for symmetry
   • Keep the polygon count low if it is for a game
   Model answer

   I would start from a cube and scale it flat to make the seat. Then I would extrude the four corner faces on the bottom downwards to make the legs, and extrude a strip along the back edge upwards to make the backrest. Loop cuts would add edges where I need more detail, and a mirror modifier would keep both sides identical. If the chair were for a game, I would keep the polygon count low.

2. • Raising the polygon count adds detail
   • But the game must draw about 60 frames a second, so too many polygons cause lag
   • Textures can fake detail cheaply
   • Better lighting and materials improve realism
   • Distant characters can use simpler models
   • Faster hardware, such as graphics cards, helps
   • A film has hours per frame, so the comparison is limited by time
   • A reasoned conclusion
   Model answer

   The studio could raise the polygon count to add detail, but a game must draw about 60 frames every second in real time, so too many polygons would make it lag. A better approach is to use detailed textures, which fake detail cheaply, along with realistic materials and lighting. Characters far away from the camera could use simpler models, saving power for the ones close up, and newer graphics cards can handle more detail each year. However, a film can spend hours on each frame using a render farm, so the limit is time, not talent. Overall, the studio can get close to film quality with clever texturing and lighting, but it cannot match a film exactly while the game still runs smoothly.

This or That

1. 6 A cube has 6 faces, 8 vertices and 12 edges.
2. A single point with x, y and z coordinates A vertex is a point. A flat surface enclosed by edges is a face.
3. An edge An edge is a straight line between two vertices. The mesh is the whole object.
4. Subdivide Subdividing splits faces to add detail. Extruding pulls a face outwards.
5. A primitive Primitives are the basic starting shapes, such as cubes, spheres and cylinders.
6. Loop cut A loop cut adds a ring of edges. A mirror modifier reflects one half to build the other.
7. More polygons: more detail, more power Extra polygons add detail and smoother curves, but need more processing power and memory.
8. It can be changed or removed later A non destructive modifier does not permanently change the mesh, so it can be adjusted or taken off.

Memory Match

• A 6 Vertex: A single point in 3D space
• B 3 Edge: A straight line joining two vertices
• C 5 Face: A flat surface enclosed by edges
• D 2 Mesh: All the vertices, edges and faces of an object
• E 1 Extrude: Pull a face outwards to make new geometry
• F 4 Primitive: A basic starting shape, such as a sphere