Jornadas sobre estrategias de generación de entornos colaborativos virtuales. What is/is not procedural?

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1 Jornadas sobre estrategias de generación de entornos colaborativos virtuales Modelado procedural mediante programación visual Gustavo Patow Geometry and Graphics Group (GGG) Universitat de Girona (UdG( UdG) 1 What is/is not procedural? This is a course about: Procedural modeling Procedural texturing Procedural animation A A Procedure a black-box,, with well defined input and output, for achieving a certain (small) target. Procedural approach making things by using different procedures that follow in a clearly definite order. Procedural Animation the color, sound, geometry and movement are manipulated procedurally 2 1

2 Non-procedural modeling Pick a vertex and drag it. Pick another vertex and drag it. Pick another vertex and drag it. Pick another vertex and drag it. Pick another vertex and drag it. Pick another vertex and drag it. Pick another vertex and drag it. 3 Procedural modeling First, I need a ¼ torus. Copy and paste, and then rotate it 180 degrees, I got another side. Merge them together I got the basic shape. The basic shape is then copied to every point on a 16x16 grid, each rotate either 0 or 90 degrees, decided randomly. 4 2

3 Non-procedural approach Need craftsmanship skill. Not much planning. Animator sits in front of the computer, fine-tune here and there, until s/he feels satisfy. Usually cannot reproduce the same result if you ask him/her to do it again. 5 Procedural approach Describes the shape/motion algorithmically. You plan a lot before you really start. Define the procedures, input and output you need. Express shape/animation as a function of parameters. You can write down the steps clearly, reproduce it anytime, or even ask others to reproduce the result. Need logical mind, careful planning, sometimes a little bit mathematics 6 3

4 Procedural approach (cont.) Easy to change any input parameters to achieve different effects. Can easily fine-tune the results in front of your client or boss. Can create results in a short time (because computer does much faster than human being). Easy to add, delete, or modify the operations at any stage. Because every steps are recorded down by the procedures. Compare to Maya s construction history? Suitable for: Large amount of geometry, each has its own variation of shape or motion (e.g. a flock of birds) Complicated shape that cannot be created by hand, but welldefined by algorithm/mathematics (e.g. plants and trees). Motions that follow physics (e.g. dynamics). Motions that follow real-world data (e.g. motion capture). 7 Effort/Timeline for both approach Non-procedural Plan Build Modify / fine-tune Procedural Plan Build Modify / fine-tune 8 4

5 Both are good I am not saying that procedural is better than non-procedural. Procedural approach can produce something that non-procedural approach cannot easily create, and vice verse. They are complement of each other. A good animation may contain both elements. A good animator should know both approach, and know when to use procedural approach, and when to use non-procedural approach. 9 The tools we ve chosen To create procedural elements, of course, programming is the best tool. However, most artists hate/afraid programming. Among existing (3D) software, Houdini is one of the best to practice the procedural idea. Houdini s workflow is based on the procedural paradigm. Reduce the programming effort to minimal. Quickly provide most common 3D elements, such as basic shape, particles, basic rendering, etc. 10 5

6 Kenneth A. Huff 11 Floyd Gillis

7 William Latham Evolutionary Art and Computer 13 Practical Introduction to visual procedural programing 14 7

8 The Houdini interface Parameters View Scene View Node Network View 15 Workflow Everything is created and modified through a network of operators (OPs) Each of them will take, or generate, some contents. The contents will be processed Then passed to the next operator for further processing. InitialShape Comp Subdiv_Facade Insert_door plain_window Repeat_Floors Repeat_Windows Exception Insert_Window 16 8

9 Ops Categories Objects (OBJ) networks of objects (geometry, light, camera, etc). Geometry (SOP) networks to construct a geometry s shape. Particle (POP) networks for particle effect. Compositing (COP2) networks for 2D compositing. Dynamic (DOP) networks for dynamic effect. Channel (CHOP) networks for channel s operation. Channel controls how a value changes over time. Shaders (SHOP) networks for creating different shaders. Output (ROP) networks for specifying the rendering settings. VEX Builder (VOP) networks for the Houdini scripting language called VEX. 17 The Network View we build our network of OPs here (i.e. procedures) to perform different tasks. press TAB and choose one of the OP available Need to remember the node name Press H to view all OPs 18 9

10 Go in and out an OP OBJ level Press u to go back to the parent level. Select and double-click an OP to go into it. SOP level 19 Information about an OP Right-click an OP and choose Help. Middle-click an OP shows the contents of this OP. Full Name: each OP has a unique name. OP type: each OP has a type (i.e. what procedure it does). Points Vertices Primitives 20 10

11 Information about an OP Points most OP contains points Points are the basic element of a 3D scene Points contains a 3D position (x,y,z), and optionally points can also contain color, normal, and other custom attribute (all called point attributes) Vertices vertices can share points, but vertices also contain their own information For example, if I have a cube with 6 different colored faces, then each corner of the cube contains 3 vertices (each vertex has a different color), but these 3 vertices share the same 3D position (i.e. shared the same point) Primitives several points form a primitive Points cannot be rendered, but primitive can Primitive is a general term in Houdini, where it can be polygons, curve surfaces (NURBS), meta-ball, etc. 21 The Scene View The Scene View is a view of your scene You can navigate this 3D view using your mouse Use SPACE + key to do different viewing ops EDIT and VIEW mode in the Scene View: ENTER ESC 22 11

12 The Parameter View When you select an operator in the Network View, the parameters of that operator will be shown in the Parameter View You can modify any editable values there 23 Our first Houdini model Step 1) Create a new Houdini file. In the OBJ level, press TAB and create a GEOMETRY (geo) Double-click the newly created geometry to go into it In the Network View, select and delete the default FILE OP that was created for you

13 Our first Houdini model Step 2) In the Network View, press TAB and create a TORUS Set the orientation of the torus to Z-axis Display/render flag: Turn it on to view the result in the Scene View One and only one display flag can be turned on inside a SOP network. 25 Our first Houdini model Step 3) Create a SPHERE OP Increase its radius to 5 try middle-drag the parameter name Radius to see what happen Also select Polygon as its primitive type We want the SPHERE to be made up by many points (and those points will be passed to the next OP) A primitive sphere will only contain one point its center 26 13

14 Our first Houdini model Step 4) Create a COPY OP and connect the network and see what happens! 27 Copy SOP Copies the shape on the left input to every point on the right input By default, the z-axis of the LHS shape will be oriented to match the normal of the points on the RHS that s why we set the orientation of the torus to z-axis If available, uses the point normal to orient the copies 28 14

15 Pre-view Render Right-click and choose View: Mantra 29 Create lights Click the Point Light button on the Shelf In the OBJ level you should find a new object (a Point Light) created 30 15

16 Assigning materials To assign material to an object: 1. Create one material in the SHOP level. 2. Assign a SHOP material to an object in the OBJ level. Or drag it from the material palette!! Left-drag to the model 31 Assigning materials You can check the result by: Go to the SHOP level: you should find a new OP created You can fine-tune the color here. Go to the OBJ level, and select your model. In the Parameter Pane, select Material You should find the full name of the SHOP material be put there

17 A Simple Animation Let s setup a simple procedural animation For example, let s make the TORUS rotate according to a cyclic formula: the sine() formula 33 A Simple Animation Select the TORUS. Right-click at its output pin, and then type TRANSFORM A new TRANSFORM OP should be created and connected between TORUS and COPY

18 A Simple Animation In the Parameter Pane, type the following formula inside the Rotate-X attribute of the TRANSFORM OP: sin($ff*5)* A Simple Animation Play the scene to see what happen You may also want to turn on the real time playback to have an idea how fast the animation is in the final rendered Real-time playback Click this to change the length of the animation if you want

19 Final Rendering (1) Move the view (2) Ctrl+left click the camera shelf button (3) A new camera object will be created 37 Final Rendering (1) Choose a camera (2) Lock camera (3) Navigate through the selected camera 38 19

20 Final Rendering To render a sequence of images, you should also create an Output driver in the OUT level Go to the OUT level, press TAB in the Network View and create a MANTRA OP Tune the rendering settings in the Parameter Pane 39 Final Rendering Change this section if you want to render a sequence of images Specify the image(s) name and file format. The $F4 in the file name will be replaced by the frame number, padded with 4 digits Change this section if you want to render in a different resolution Make sure that you are in the OUT level Lastly, you can click the RENDER button on the upper-left corner of the Parameter Pane to start the final rendering 40 20