Announcements

1. Announcements • Prototype submissions will be directly from SVN on Gforge • We will just grab your last commit before due date • Has to work (always maintain a working build on SVN) Evaluation Criteria Working game Milestones for individual members Commenting (SVN logs and in code) Daily logs

2. 2D to 3D • Many current games use 3D graphics • Much more complex than 2D graphics • This course will provide a basic overview of 3D graphics • CMPS 160, 161, 164 provide greater depth Ratchet and Clank

3. 3D Camera • Analogy • 2D is like putting stickers on a page • Place sticker (sprite) at x,y coordinate • If a sticker is placed at 50,50, you see it • 3D is like recording a video with a camera • What is recorded (shown on screen) is what camera sees • Can have objects in a scene that aren’t visible • Can have 3D object at 50,50,50, but if camera is pointing in the opposite direction, won’t see it! • Introduces rotation • Camera can potentially be rotated around all 3 axes • Objects can also be rotated around 3 axes • Affects what shows up on screen

4. 3D Coordinate System • 3D graphics requires use of x,y,z coordinates • So, which direction is positive z? • Is it back away from you, or towards you? • Either choice would work, need to pick one • Right handed vs left handed coordinate systems • XNA uses right handed coordinate system • Place hands, palms up • Point fingers in direction of positive X • Curl fingers in direction of positive Y • Thumb is pointing in direction of positive Z Right-handed coordinate system

5. Camera • Camera is comprised of two Matrix objects • View matrix holds information on • Location of camera in world • Camera direction • Camera orientation • Projection matrix holds information on • View angle • Aspect ratio • Near and far plane Direction Location (x,y,z) Orientation

6. Matrix Structure • XNA provides a Matrix structure • A 4x4 matrix, in row vector layout • Row vector matrices view vectors as a row from left to right • column vector matrices view vectors as a column from top to bottom • Built-in matrix operations • +, -, *, /, == • Also, convenience matrices • Identity, Up, Down, Left, Right • Large number of convenience methods • Rotations, views into 3D world, determinants, invert

7. Vector3 Structure • Represents either: • An X, Y, Z coordinate, or, • Distances along X, Y, Z coordinates (e.g., a vector) • Often a unit vector • all values between 0 and 1 • X, Y, Z properties (floats) • Built-in operators • +, -, *, /, ==, != • Convenience vectors • UnitX, UnitY, UnitZ, Up, Down, Left, Right • Many convenience methods • Interpolations, rotations, distance, dot product, normalization (x,y,z) coordinate y (x,y,z) vector x z

8. Creating an XNA Camera – View Matrix • View matrix • Use CreateLookAt method of Matrix structure • Parameters (all Vector3) • cameraPosition – location of camera (x,y,z) • cameraTarget – coordinate of point where camera is looking • cameraUpVector – vector indicating up position cameraUpVector cameraTarget (x,y,z) cameraPosition (x,y,z)

9. Creating an XNA Camera – Projection Matrix • Projection Matrix • Use CreatePerspectiveFieldOfView method • Parameters (all floats) • fieldOfView – angle of camera view, in radians • Typically 45degrees – pi/2 radians • aspectRatio • Typically width of screen divided by height of screen • nearPlaneDistance • Distance from camera to near viewing plane • Objects between camera and near plane are not shown! • farPlaneDistance • Distance from camera to far viewing plane • Objects beyond far plane are not shown! cameraPosition (x,y,z)

10. Drawing Triangles • All complex 3D shapes seen in games are composed of a series of triangles • A triangle has 3 points, one for each corner • Points are more typically known as verticies • Minimum number of points to unambiguously define a plane • VertexPositionColor object • Represents the x,y,z location of a vertex • Also has a color for the vertex • VertexPositionColorv = new VertexPositionColor(new Vector3(0,1,0), Color.Blue); • Need 3 verticies to draw a triangle

11. Vertex Declaration • XNA requires you to tell the graphics device what kind of vertex data you will be using • Was unclear why XNA couldn’t figure this out in 3.0, or handle multiple types seamlessly and is has been improved in 4.0 • Probably due to structure of DirectX API, or capabilities of graphics hardware • For now, treat as a must-do, black box • Put following in your main, derived from Game class • GraphicsDevice.VertextDeclaration = new VertexDeclaration(VertexPositionColor.VertexElements); • IVertexType implementation

12. Actually drawing the triangles • In XNA, all 3D rendering is handled by a shader • Shaders defined using High Level Shader Language (HLSL) • Permits creation of wide range of visual effects • More on shaders in a few classes • XNA provides a default shader • Called BasicEffect • Will use this for now • BasicEffect is a type of effect • Effects contain a series of EffectPass • Each pass handles some aspect of putting things on screen

13. Using Basic shader • Five steps • Create Shader • Copy over camera information • Iterate through EffectPasses • Examine source code from example in Chapter 9 of XNA 3.0

14. Using Basic shader Five steps: • Create Shader • BasicEffect effect = new BasicEffect(GraphicsDevice, null); • Copy over camera information • effect.View = camera.view; • effect.Projection = camera.projection; • Set world matrix • effect.World = …(more on this in a few slides) • Enable vertex capabilities (varies by Vertex type) • Effect.VertexColorEnabled = true; // for VertexPositionColor • Effect.Texture = myTexture; // for VertexPositionTextureEffect.TextureEnabled = true; • Iterate through EffectPasses • Call to DrawUserPrimitives inside EffectPass puts triangles on screen

15. Iterating Through Effect Passes • Each Effect has calls to begin()/end() • Effects are comprised of passes • Each pass requires a call to begin()/end() effect.Begin(); foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Begin(); GraphicsDevice.DrawUserPrimitives<VertexPositionColor> (PrimitiveType.TriangleStrip, verts, 0, 1); pass.End(); } effect.End(); Passes Draws verticies # of triangles (the “primitive shape” in this context) to draw Index into verts array

16. Triangle Drawing • Examine this line of code • GraphicsDevice.DrawUserPrimitives<VertexPositionColor> (PrimitiveType.TriangleStrip, verts, 0, 1); • What is a TriangleStrip? • Three ways to draw triangles • Triangle List • Each set of three verticies defines a triangle • Memory inefficient, since triangles often share edges in complex 3D meshes • Triangle Strip • Builds triangle out of first three verticies • Each additional vertex creates new triangle using that vertex, plus previous two verticies • Triangle Fan • Each additional vertex creates new triable using that vertex, the previous vertex, plus the first vertex http://escience.anu.edu.au/lecture/cg/surfaceModeling/image/surfaceModeling015.png

17. World Matrix • Each triangle has 3 verticies, and each vertex has an x,y,z position • This position is given with respect to an origin location • That is, location is with respect to a local coordinate system • World matrix • Translates from the local coordinate system to the world (i.e., visible on screen) coordinate system local world Local coordinate system offset, no rotation(Note: example uses left handed coordinate system, XNA uses right-handed coordinates) Source: MSDN DirectX documentation Local coordinate system offset and rotatedwww1.adept.com/main/KE/DATA/V%20Plus/V%20Language%20User/images/World+yaw.gif

18. Translation • A translation shifts the local coordinate system relative to the world coordinate system • XNA provides a method for this • Matrix.CreateTranslation • 3 parameters are x,y,z movements • Matrix.CreateTranslation(0.01f, 0, 0); // Shift right (positive) along x axis • Matrix.CreateTranslation(-0.01f, 0, 0); // Shift left (negative) along x axis • Multiply world matrix by translation matrix to cause shift • All translations and rotations in 3D graphics accomplished via matrix multiplication

19. Rotation • A rotation shifts the local coordinate system by an angle relative to the world coordinate system • XNA helper methods • Matrix.CreateRotationX, Matrix.CreateRotationY, Matrix.CreateRotationZ • Rotations around single axes • Matrix.CreateRotationY(angle in radians); • Matrix.CreateFromYawPitchRoll • Rotate around multiple axes • Matrix.CreateFromYawPitchRoll(yaw rad., pitch rad., roll rad.) • Demonstration of example triangle drawing code

20. Triangles are fine, but models are better • Today’s 3D games have a large number of objects • Theoretically possible to create these objects by manually writing C# code to create each individual triangle • In practice, this is rarely done. • Far better to use a 3D modeling tool • Maya, XSI, 3DS Max, Blender • Allows artists to create objects in world • Allows programmers to focus on behavior of objects • Modeling tools permit much faster creation and editing of models

21. 3D Modeling • Several ways to model a 3D object • Polygonal modeling • Objects are subdivided into a series of polygons (triangles) • Can only approximate curved surfaces • Dominant modeling form in computer games and computer graphics due to speed of rendering • NURBS • Surfaces are defined by spline curves • Curves defined and controlled by control points • Splines and patches • Curved lines define surfaces. Between polygons and NURBS • Primitives modeling • Objects built up from primitive shapes (balls, cubes, cylinders, etc.)

22. 3D Model formats • There is a huge number of 3D model formats • No dominant standard • Interchange among models is often lossy • XNA supports two 3D model formats • .X (DirectX) • .FBX • Originally for FilmBox by Kaydara, then Alias, now Autodesk

23. Models in XNA • Model • Represents some entity • A person, a car, or potentially a complex scene with many parts • Typically used to represent one logical object (e.g., a person) that has multiple parts (head, arms, legs, etc.) • A model contains multiple meshes and bones • Mesh • Represents a single physical object • Triangles, textures, shaders, etc. • XNA ModelMesh class • Bone • Represents placement of each mesh relative to other meshes • A transformation matrix Model 1 1 N N ModelMesh Bone Car Body+bone Wheel+bone Door +bone

24. Models in XNA (cont’d) Model 1 1 • ModelMesh contains: • List of ModelMeshPart • List of Effects • Verticies for triangles that comprise this mesh • VertexBuffer • Also has a bounding sphere • ModelMeshPart • Represents a set of triangles that share the same materials (e.g., shader, or Effect) • Has indexes into the ModelMesh • Starting index, number of triangles, number of primitives to use from parent ModelMesh’s VertexBuffer N N ModelMesh Bone 1 1 1 N 1 N Effect VertexBuffer ModelMeshPart 1 1 1 1 1 N 1 1 StartIndexNumVerticiesPrimitiveCount Effect Verticies

25. Working with Models in XNA • Bring model into XNA project inside Visual Studio • Load model into XNA via Content manager • Draw model by iterating through all contained meshes

26. Importing Models into Visual Studio • Import model into Content directory • Copy .x or .fbx file, along with associated texture images, into Content directory in XNA project • Inside Visual C#, right-click on Content directory • Add… Add Existing Item • Select .x or .fbx file • Similar process to adding bitmap textures, etc.

27. Loading Model via Content manager • Models are loaded via the content manager • Model model = Content.Load<Model>(@”{name of my model without .x or .fbx extension}”) • XNA parses the model file, and fills in verticies, textures, and effects in Model, and ModelMeshes • In XNA, this is a robust operation, big time savings • In many open source 3D game engines, model import can be a big problem • At present, typically is not safe to assume model import will work smoothly in a given 3D game engine • Need to test your tool chain

28. Drawing a Model • Iterate through all of the meshes • Iterate through each effect for each mesh • Set lighting, camera, and world for each effect • Draw each mesh using Draw() method on ModelMesh class foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect be in mesh.Effects) { be.EnableDefaultLighting(); be.Projection = camera.projection; be.View = camera.view; be.World = world * mesh.ParentBone.Transform; } mesh.Draw(); } • Examine example code from Chapter 10 of Learning XNA 3.0

29. More on Models • Explanation of parts of XNA models • http://blogs.msdn.com/shawnhar/archive/2006/11/20/models-meshes-parts-and-bones.aspx