Visualization and Simulation

Visualization and SimulationCaio Brito

Summary

• Local Illumination– Graphical pipeline– Illumination model– Shader

• Global Illumination– Ray Tracing– Path tracing

• Physics based simulation– Fluids– Rigid Body– Position-Based

Local Illumination

Local Illumination :: Graphical Pipeline

Local Illumination :: Graphical Pipeline

Local Illumination :: Illumination Model

Local Illumination :: Illumination Model

• Ambient– Simple way of modeling indirect reflection.

Ia: Ambient light intensity

Ka: Ambient constant

Local Illumination :: Illumination Model

• Diffuse– Ideal diffuse surface reflects light equally in all directions,

according to Lambert's cosine law.

– Lambert’s Cosine Law: amount of light energy that falls on surface and gets reflected is proportional to incidence angle.

Local Illumination :: Illumination Model

• Diffuse– Smaller angle > Bigger cosine > More intensity.

Local Illumination :: Illumination Model

• Specular– Simulates a highlight.– Reflection angle = incident angle.

Local Illumination :: Illumination Model

Local Illumination :: Illumination Model

• Flat Shading– Shades each polygon of an object based on the angle

between the polygon's surface normal and the direction of the light source.

Local Illumination :: Illumination Model

• Gouraud Shading– Calculates the surface normals for the polygons.– Lighting computations are then performed to produce

intensities at vertices.– These intensities are interpolated along the edges of the

polygons.

Local Illumination :: Illumination Model

• Phong Shading– Calculate the surface normals at the vertices of polygons in

a 3D computer model.– These normals are interpolated along the edges of the

polygons.– Lighting computations are then performed.

Local Illumination :: Illumination Model

Position-Normal Distributions for Efficient Rendering of Specular Microstructure

Local Illumination :: Illumination Model

Physically-Accurate Fur Reflectance: Modeling, Measurement and Rendering

Local Illumination :: Illumination Model

Discrete Stochastic Microfacet Models

Local Illumination :: Shader

• A Shader is a user-defined program designed to run on some stage of a graphics processor.

• Its purpose is to execute one of the programmable stages of the rendering pipeline.

• GLSL, HLSL, Cg, DirectX• Basic structure: Vertex Shader and Fragment Shader• http://antongerdelan.net/opengl/• https://learnopengl.com/• https://www.shadertoy.com/

Local Illumination :: Shader

• Vertex Shader

Local Illumination :: Shader

• Fragment Shader

Local Illumination :: Shader

• Fragment Shader

Local Illumination

Global Illumination

Global Illumination

• Local Illumination

• Global Illumination

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

• Primary Rays– Primary rays are rays from the viewpoint to the nearest

intersection point.– Local illumination is computed:

Global Illumination :: Ray Tracing

• Secondary Rays– Reflection Ray

Global Illumination :: Ray Tracing

• Secondary Rays– Refraction Ray

Global Illumination :: Ray Tracing

Global Illumination :: Ray Tracing

• Limitation

Global Illumination :: Ray Tracing

• Limitation

Global Illumination :: Path Tracing

• Trace multiple rays from a single pixel

Global Illumination :: Path Tracing

• How to choose a secondary ray?• Each material have a Kd, Ks and Kt

– Let Ktot = Kd + Ks + Kt– Choose a random number R in the interval (0,Ktot)

• If (R < Ks), trace a diffuse ray• else if (R < Kd + Ks), trace a specular ray• else, trace a refraction ray

Global Illumination :: Path Tracing

Global Illumination :: Path Tracing

Global Illumination :: Path Tracing

Which Realism?

• Photorealism – image produces the same visual response as the scene

• Functional realism– Image provides the same visual information as the scene

Which Realism?

• Photorealism

Which Realism?

• Functional realism

Physics Based Simulation

Physics Based Simulation :: Fluid Simulation

• Smoothed Particle Hydrodynamics– Solve Navier-Stokes equation– Finite number of particles

• Position, velocity, mass, density, viscosity and influence radius

Physics Based Simulation :: Fluid Simulation

• Smoothed Particle Hydrodynamics

Physics Based Simulation :: Fluid Simulation

• Smoothed Particle Hydrodynamics

Physics Based Simulation :: Fluid Simulation

• Smoothed Particle Hydrodynamics

Physics Based Simulation :: Fluid Simulation

• Smoothed Particle Hydrodynamics

Physics Based Simulation :: Rigid Body Dynamics

• Rigid bodies have a position and orientation• No deformation• The motion be represented by 2 parameters

– Center of mass– Orientation

• Force and Torque are computed

Physics Based Simulation :: Rigid Body Dynamics

Physics Based Simulation :: Position-Based Dynamics

• Particles everywhere– Position, velocity, mass, phase

• Uses different constraints for each kind of simulation– Distance (clothing) – Shape (rigids, plastics) – Density (fluids)– Volume (inflatables)– Contact (non-penetration, friction)

Physics Based Simulation :: Position-Based Dynamics

Physics Based Simulation

Visualization and SimulationCaio Brito