Modelling Techniques PDF

Modelling Techniques 3D Modelling Games and Multimedia Authors: Alexandrino Gonçalves and Nuno Rodrigues Last revision: 2/10/2024  Computer Modelling Normally, modelling start with sketches or blueprints The conceptual...

Modelling Techniques 3D Modelling Games and Multimedia Authors: Alexandrino Gonçalves and Nuno Rodrigues Last revision: 2/10/2024  Computer Modelling Normally, modelling start with sketches or blueprints The conceptualization and design of the 3D model is the first stage in the simulation of a 3D scene From an artist point of view this step is the most important one: Shapes, position, sizes, colours, textures, lights, camera, etc. It is at this stage that the best modelling techniques are chosen to achieve the desired results 3DM 2  Modelling Process Types Curve modelling - Surfaces are defined by curves. Curve types include splines, Bézier, nonuniform rational B-spline (NURBS), etc. Polygonal modelling - Shape mesh created by polygons. Since polygons are planar, it can only approximate curved surfaces by using a large number of polygons. Digital sculpting – A more recent method of modelling. The artist create the 3D model using tools to push, grab, pull, smooth or pinch, usually using a pressure-sensitive device to mould the object. 3DM 3  Curve Modelling Lines can be used to define the shape of an object and many of its surface characteristics Curved lines can be used to define curved surfaces, and build meshes of curved surfaces Curves are also often called splines 3DM 4  Curve Modelling There are different types of curves They are classified based on their mathematical and geometrical features They are created and controlled by a set of control points or control vertices Most used in 3D modelling: - Bézier - B-Spline - NURBS (Non-Uniform Rational B-Spline) 3DM 5  Bézier A Bézier curve is defined by a set of control points These curves can be Linear (2 control points) 3DM 6  Bézier Quadratic (3 control points) Cubic (4 control points) 3DM 7  Bézier Higher orders (5 or more control points) 3DM 8  B-Spline A B-spline (basis spline) curve is similar to bézier with additional information between the control points 3DM 9  NURBS Non-Uniform Rational Basis Spline (NURBS) is a mathematical model commonly used in modelling for generating and representing curves and surfaces NURBS curves and surfaces are generalizations of both B-splines and Bézier curves Nowadays it is a standard method heavily used in the automotive and industrial modelling (CAD) 3DM 10  NURBS A NURBS curve is defined by: Its order A set of weighted control points A knot vector 3DM 11  NURBS NURBS can be used to create 3D surfaces (which can be later converted to a mesh) by using two or more curves in a 3D space. Control vertices allow manipulation along the X, Y or Z axis 3DM 12  Polygonal Modelling Standard geometric primitive shapes: Cube Sphere Cylinder Cone Torus Regular polyhedral (tetrahedron, octahedron, etc.) Present in all 3D modelling software 3DM 13  Primitive Modelling Model 3D objects using only standard geometric shapes (cubes, spheres, cylinders, etc.) Done by applying geometric transformations to the primitives 3DM 14 Primitive Modelling 3DM 15  Logical (Boolean) Operators Used to create 3D models by adding and subtracting shapes in a variety of ways Operations: Union Intersection Difference 3DM 16  Logical (Boolean) Operators Union 3DM 17  Logical (Boolean) Operators Intersection 3DM 18  Logical (Boolean) Operators Difference (useful for creating holes) 3DM 19  Logical (Boolean) Operators How to create this shape? 3DM 20  Logical (Boolean) Operators How to create this shape? 3DM 21  Box/Subdivision Modelling The artist start with a low-resolution primitive (cube, sphere, cylinder, etc.) Achieve the desired appearance by applying successive shape refinements: Interpolating Averaging Approximation Insertion of new points Usually ends with a high poly object 3DM 22 Box/Subdivision Modelling Example: https://www.youtube.com/watch?v=-Ft4ljD1Icg 3DM 23  Mirroring Technique As seen in the (video) previous technique, to ease the modelling, we can model just a section of a symmetrical object and mirror it in any axis or specific point 3DM 24  Edge/Contour Modelling In edge modelling the object is built piece by piece: Placing polygonal faces along prominent contours Filling any gaps that eventually occur Example: https://www.youtube.com/watch?v=CRWJ9Ecw7DQ 3DM 25  3D Scanning 3D Scanning is a method of digitizing real-world objects A real-world object can be scanned, and all the geometric data obtained (x, y, z point cloud) is used to generate an accurate polygonal mesh Textures can also be obtained using this method Microsoft Kinect 2 (discontinued) 3DM 26 3D Scanning 3DM 27  3D Scanning Moinho de Papel Museum (Leiria) 3DM 28  3D Scanning Moinho de Papel Museum (Leiria) 3DM 29  3D Scanning Moinho de Papel Museum(Leiria) 3DM 30  3D Scanning Museum of Conimbriga 3DM 31  3D Scanning Carsoscópio 3DM 32 Photogrammetry 3DM 33 Photogrammetry Teste/Teste /Teste /Teste /Teste 3DM 35  Photogrammetry Allow to reconstruct 3D environments (geometry and textures) by extracting spatial information from a series of photographs of a known space Photogrammetry software virtually reconstructs the geometry of that particular space We just need to point the corners or main edges of the main shapes in the photographs 3DM 36 Photogrammetry 3DM 37 Photogrammetry Source: https://www.artstation.com/artwork/wegdY 3DM 38  Sweeping One of the most powerful modelling techniques The idea is to sweep a 2D outline along a predefined path, creating a 3D shape: Extrusion Free-form sweeping Lathe / Revolve 3DM 39  Extrusion Extrusion is a method of adding geometry to a polygon primitive It is applied to a face (or a set of faces) and creates new faces of the same size and shape In this case the path is the surface normal 3DM 40  Free-Form Sweeping Similar to extrusion but in this case the path can be a curved line This particular extrusion can be done along any axis or combination of axis 3DM 41  Lathe / Revolve This technique sweeps a 2D outline (closed or not) around one axis Used in surfaces with geometric symmetry It requires the angle of rotation and the number of facets 3DM 42  Procedural Modelling Generate automatically 3D geometry using an algorithmic procedure Increase productivity since manual modelling of such shapes is very time consuming Suited for indie game developers Heavily used in films, animation and videogames 3DM 43 Procedural Modelling in Videogames Rogue (1980) Diablo (1996) 3DM 44  Procedural Modelling in Videogames Minecraft Source: Endless worlds, realistic worlds: procedural generation and artificial intelligence in video games (2022) (https://business.blogthinkbig.com/realistic-worlds-procedural-generation-artificial-intelligence-video-games) 3DM 45  Procedural Modelling Can be used to create: Buildings Fire Vegetation Explosions Terrains Textures Clouds Etc. Water 3DM 46 Procedural Modelling - Buildings Conimbriga 3DM 47 Procedural Modelling - Buildings Buildify (Blender addon) 3DM 48 Procedural Modelling - Fractals Fractals are random and irregular shapes found in nature Create models difficult to obtain with geometric modelling It can be applied to: Existing 3D meshes Create an entire new models 3DM 49 Procedural Modelling - Fractals Fractals are: Found in nature Mathematical Recursive Patterns repeated Describe processes in time Subdivided into levels of recursion 3DM 50 Fractals Found in Nature 3DM 51 Procedural Modelling - Fractals Trees 3DM 52 Procedural Modelling - Fractals Landscapes Example: https://www.youtube.com/watch?v=bifdKWzMwI8 3DM 53 Procedural Modelling - Fractals "It so happens that I'm a lazy animator." Julius Horsthuis 3DM 54 Procedural Modelling – Particle System Used to simulate natural phenomena like: Fire, explosions, smoke, rain, snow, … Hair, fur, grass, … Based on employing simple shapes (spheres, points,…) in the 3D space These shapes/particles have a specific behaviour through time 3DM 55 Procedural Modelling – Particle System They have a life time during which they behave a certain way and then fade away or merge with other particles Usually a particle system need to define: Number of particles Lifetime Randomness Emitter Normal 3DM 56 Procedural Modelling – Particle System Firstly used by William Reeves (Lucasfilm) in Star Trek II - The Wrath of Khan (1982) 3DM 57 Procedural Modelling – Particle System 3DM 58 Procedural Modelling – Particle System Fur/Hair 3DM 59 Procedural Modelling – L-Systems Formal grammar: Alphabet of symbols Production rules Parallel rewriting system 3DM 60  L-Systems G = (V, ω, P) V: Alphabet ω: Axiom (where it starts) P: Production rules Example: V: A, B ω: A P: A→AB; B→A 3DM 61  L-Systems Exercise Write the first 6 iterations of the grammar: G = (V, ω, P) V: A, B ω–A P – A→AB; B→A 3DM 62 Procedural Generation - Textures Miróbriga Roman Ruins (Santiago do Cacém) 3DM 63 Procedural Modelling in Videogames Example (Houdini): https://www.youtube.com/watch?v=qjDv_0W77Dk 3DM 64  Geometry Nodes Nodes are blocks that contain data that, in a procedural workflow, transform inputs into outputs based on user- defined parameters Geometry nodes allow altering the geometry of an object as well as making other specific modifications Widely used in Blender (and Houdini) It starts with the Group Input node (the starting state of the object) and ends with the Group Output node, which is the outcome of all the procedures defined by the intervening nodes 3DM 65  Geometry Nodes Once a group node is created, the modifier can be saved and applied to other objects, saving time in the modelling process It also makes the workflow more efficient, minimizes common errors, and increases scalability 3DM 66  Landscapes Useful for real or imaginary landscape surfaces Normally, for imaginary landscapes, we start with a 2D plane with several subdivisions, and: Direct point manipulation Mathematical (procedural) functions 3DM 67  Landscapes – Real Surfaces Contour (using their topological data) 3DM 68  Landscapes – Real Surfaces Height/displacement maps 3DM 69  Landscapes – Real Surfaces Height/displacement maps Example: https://www.youtube.com/watch?v=52Eil_rf4c4 3DM 70  Beveling Smooth sharp edges between adjacent facets Controlled by distance, radius or angle value 3DM 71  Digital Sculpting Digital sculpting is the use of software and hardware (tablet and pen) to digitally manipulate an object as if it were made of a real-life substance such as clay Common operations: Push Pull Smooth Grab Pinch... 3DM 72  Digital Sculpting Main applications: Blender ZBrush Mudbox Cinema 4D 3D Coat Maya 3DM 73  Digital Sculpting Digital sculpting tools: Mouse Pen tablet → pressure sensitivity Haptic input devices Example: https://www.youtube.com/watch?v=Lso8KitmchY 3DM 74