Phong MAT

From TouchDesigner 099 Wiki

Summary

The Phong MAT creates a material using the Phong Shading model. It has support for textures, reflections, bumps, cone lights, rim lights, alpha maps and more. You can output its GLSL shader into two DATs for further adaptation in a GLSL MAT by using the Output Shader parameter.

Phong Shading models three types of reflected light:

  • Ambient - Ambient is considered light that does not come from any particular direction and is therefore constant across the surface. In the physical world, ambient light is created from the reflection of light off surfaces in the environment.
  • Diffuse - Diffuse models the light reflected by matte surfaces. This light is reflected equally in all directions, therefore the position of the observer does not effect the percieved illumination.
  • Specular - Specular models the light reflected by glossy surfaces. This light is reflected mainly in the direction of the reflected ray and is attenuated by the 'shiny-ness' of an object. Since the light reflected from the surface is mainly in the direction of the reflected ray, the position of the observer determines the specular highlight on the surface.

NOTE: We see the color of an object because of the color of light that the material reflects.

Phong Shading produces very nice specular highlights, although it is still an approximation and not physically accurate. Contrasting with the Gouraud shading model that calculates the lighting at each vertex and interpolates the value across the polygon, Phong calculates the lighting at each pixel.

To see how all of the different parts are summed together by looking at the Phong Lighting Equation article.

PythonIcon.png phongMAT_Class

Parameters - RGB Page

Ambient uses Diffuse ambdiff - Uses the Diffuse parameter for Ambient when checked.

Diffuse diff - The color of the diffuse light reflected from the material.

Ambient amb - The color of the ambient light reflected from the material.

Specular spec - The color of the specular light reflected from the material. This changes the color of the highlights on shiney objects.

Emit emit - This is the color that the material will emit even if there is no light.

Constant constant - Adds to the final color. Where there are point colors, finalcolor += Point Color * Constant Color. This behaves like there is ambient illumination of 1 1 1. It is not affected by textures or transparency.

Shininess shiniess - Controls the specular highlights (glossyness) of an object. Higher settings are more glossy, like plastic or shiny metal. Lower settings give more of a matte finish.

Color Map colormap - Specifies a TOP texture that is multiplied by the results of all of the lighting calculations. The alpha of this map is used as a part of calculating the objects alpha. Clicking on the arrows to the right of the map field will open the Texture Sampling Parameters for Color Map. The other Map parameters below will have their own Texture Sampling Parameters as well.

Normal Map (Bump) normalmap - Uses a Normal Map from TOPs to create a 'bump map' effect. Bump-mapping simulates bumps or wrinkles in a surface to give it a 3D depth effect. Your geometry must have tangent attributes created for this feature to work (T[4]). Create these using the Attribute Create SOP.

Bump Scale bumpscale - A multiplier for the 'bump effect' created by the Normal Map parameter.

Parallax Mapping parallaxmapping - Enable parallax mapping. Must be used in conjunction with a normal map.

Parallax Clamp parallaxclamp - Clamp the parallax shift to a certain value. Parallax shift refers to the calculated offset of the mapped textures.

Diffuse Map diffusemap - Specifies a TOP that multiples the Diffuse Color. The object must have texture coordinates. The alpha of this map is ignored.

Specular Map specmap - Specifies a TOP texture that is multiplied with the Specular color parameter of the material. The object must have texture coordinates. The alpha of this map is ignored.

Emit Map emitmap - Specifies a TOP texture that is multiplied with the Emit color parameter of the material. The object must have texture coordinates. The alpha of this map is ignored.

Environment Map envmap - Uses a TOP texture to define an environment map for the material. Environment mapping simulates an object reflecting its surroundings. The TOP defined in this parameter is the texture that will be reflected. The Env Map is added to whatever the normal lighting will be, so to make an object purely reflective turn the Diffuse and Specular parameters to 0. This input expects a sphere map. An example of a sphere map can be found here. This input will also accept a cube map, created with the Cube Map TOP or the Render TOP's Render Cube Map parameter.

Environment Map Color envmapcolor[rgb] - This color is multiplied with the texture specified by the Environment Map parameter above.

Environment Map Rotate envmaprotate[xyz] - Rotate the texture specified by the Environment Map parameter above.

Polygon Front Face's frontfacelit - Controls how the polygon's normal is used to light the front face of the polygon. For more information refer to the Two-Sided Lighting article.

Polygon Back Face's backfacelit - Controls how the polygon's normal is used to light the back face of the polygon. For more information refer to the Two-Sided Lighting article.

Output Shader... outputshader - This button will bring up a dialog that will create a GLSL MAT and Text DATs with shader code that matches whatever effect this Phong MAT is currently creating. Since shaders are dependent on the number and type of lights, it will list some possible different shader choices, based on what lighting configurations have been used in the current system. If no shaders are listed in the dialog, it means no shader has been rendered in the current session of TouchDesigner. Turn on the viewer for the Phong MAT, or setup a render in a Render TOP. That will create/compile some shaders and will cause the list to be populated. For example if you want to see a shader that does shadow mapping, setup a render that does shadow mapping and you will see that come up in the list.

Parameters - Alpha Page

Note: Simply applying alpha to an object does not make it transparent. For more information refer to the Transparency article.

Alpha Map alphamap- This map multiplies the alpha of the object. It uses the red channel of the map, other channels are ignored.

Uniform Alpha alphamode - Turning this off will make the alpha change depending on orientation of each polygon's normal compared to the camera. Normals that are pointing at the camera will results in the polygon having an alpha of Alpha Front. Normals that are perpendicular to the camera (facing sideways/up/down) will have Alpha Side for their alpha.

Alpha Front alphafront - The opacity of the material. This parameter is multiplied by point alpha of the object (as will as any other alpha source).

Alpha Side alphaside - This is used for non-uniform alpha. It is the alpha value polygons that are facing away from the camera will get.

Alpha Rolloff rolloff - Controls how the alpha changes from Alpha Front to Alpha Side.

Post-Mult Color by Alpha postmultalpha - At the end of all of the calculations, the color (RGB) is multiplied by the calculated alpha. You can stop this from happening by turning off this toggle.

Mult Alpha by Light Luminance alphamultlight - When this is enabled, the luminance of the lighting will be multiplied by the alpha, to decrease/increase it.

Parameters - Multi-Texturing Page

On the Multi-texturing page of the Phong material, you can have up to 4 texture maps and choose any of the 8 possible texture coordinates for each map. By default the texture maps are multiplied together, but there is a field for a custom GLSL code that can be used. Here's how that works:

The 4 texture maps are referred to in the parameter by t0, t1, t2 and t3 respectively. So the default equation if all 4 texture maps are used is: t0 * t1 * t2 * t3. You can use and constants and other math operators, so for example t0 + (t1 * 0.5) is valid. If they refer to a map that doesn't exist, the shader won't compile correctly (e.g. using t3 when it isn't set or the TOP doesn't exist).

They can also refer to specific components of the texture using .r .g .b and .a. So for example if you want to do t0 over t1, the expression would be:

t0 + (t1 * (1.0 - t0.a))

The output from your expression must be a vec4, so for example:

 t0.rgb + t1.rgb // Error
 vec4(t0.rgb + t1.rgb, 1.0)  // Works

The alpha from the result of these maps is used.

Multi-Texturing (Disables Color Map) multitexturing - Enables multi-texturing. This disables the Color Map parameter.

Texture [1-4] texture1 through /texture4 - You can specify up to 4 textures for multi-texturing.

Texture Coord texture1coord through /texture4coord - Specifies which texture coordinate to use for the map.

GLSL Expression multiexpr - GLSL code that combines the texture images (look to the start of this section for more details). This parameter can be left blank (which means the maps will just be multiplied together).

Parameters - Rim Page

Other rim lights have the same parameters, internal parameter names just have a different number instead of 1.

Enable Rim Light 1 rim1enable - Enables this rim light.

Rim Map rim1map - This map will multiple the calculated rim light color.

Rim Color rim1color - The color of the rim light.

Rim Center rim1center - The center of the rim lights location, situated somewhere on a 360 degree circle.

Rim Width rim1width - How far from the center the rim light extends.

Rim Strength rim1strength - Controls the brightness of the rim light.

Rim Strength Ramp rim1strengthramp - You can specify a horizontal ramp (it will sample the texture at v = 0.5), which controls the the rim lights strength.

Parameters - Advanced Page

Shadow Strength shadowstrength - This parameter will control how much being in a shadow will change the color of the lighting. At 1 the object will take on the Shadow Color parameter, at 0 it will behave as if it's not in a shadow, even if it is.

Shadow Color shadowcolor - The color that will be used in shadowed areas.

Darkness Emit darknessemit - The Phong MAT calculates the current brightness of color of the objects, after taking into account lights, rim lights, emission etc. It then uses this brightness (between 0-1) and fades in the Darkness Emit Color. The darker the area, the more of the darkness emit color that will be applied.

Darkness Emit Color darknessemitcolor - The color that is used for areas that are in darkness.

Darkness Emit Map darknessemitmap - This map multiplies the Darkness Emit Color. This maps alpha is not used.

Darkness Emit Map Coord darknessemitmapcoord - The texture coordinate used to sample the darkness emit map.

Secondary Specular spec2[rgb] - Adds a secondary specular highlight color.

Secondary Shininess shininess2 - Controls the secondary specular highlights (glossyness) of an object. Higher settings are more glossy, like plastic or shiny metal. Lower settings give more of a matte finish.

Write Camera Space Depth To Alpha writecameradepthtoalpha - This cause the camera space depth of the pixel to be written to the alpha channel of the output TOP. This value can be useful for post-processing effects, but ofcourse you will not have the result of all the alpha calculations if you turn this on (although they'll get used to multiply the output color, assuming Post-Mult Color by Alpha is enabled.

Apply Point Color applypointcolor - Normally the color attribute (Cd[4]) coming from the SOP is used in the lighting calculation, you can turn off using the color attribute by un-checking this parameter.

Instance Texture instancetexture - When provider per-instance textures in the Geometry COMP, this parameter selects which map the instance texture will be applied as.

Color Buffer [1-7] RGB colorbuffer[1-7]rgb - Allows sending things like normals or diffuse color to different Render TOP color buffers in a single pass.

Parameters - Optimize Page

Note: The features on this page are legacy and should not be needed on modern GPUs. The below parameters avoid doing extra work in the pixel shader for some vectors, resulting in faster rendering. However this can result in lighting artifacts. Try them out and see if they make a visual difference to your scene.

Each of the parameters below uses the following menu

  • Use Global Settings - Uses the global settings found in the Preferences dialog under Edit > Preferences > MATs
  • Yes - Turns the option on.
  • No - Turns the option off.

Fast Normalize Half-Angle fastnormhalfang

Don't Re-normalize Normal dontrenormnorm

Don't Re-normalize Light Vector dontrenormlightvec

Don't Re-normalize Spot Vector dontrenamespotvec

Don't Re-normalize Eye Vector dontrenameeyevec

Fast Deform Tangent <fastdeformtangent

Parameters - Deform Page

Refer to the Deform Article for more information on doing deforms in TouchDesigner.

Deform dodeform - Enables deforms on this material.

Get Bone Data: deformdata - Specifies where the deform bone data will be obtained.

SOP with capture data targetsop - Specifies the SOP that contains the deform capture attributes.

pCaptPath Attrib pcaptpath - Specifies the name of the pCaptPath attribute to use. When your geometry has been put through a Bone Group SOP, the attributes will be split into names like pCaptPath0, pCaptPath1. You can only render 1 bone group at a time, so this should match the group you are rendering with this material.

pCaptData Attrib pcaptdata - Much like pCaptPath Attrib.

Skeleton Root Path skelrootpath - Specifies the path to the COMP where the root of the skeleton is located.

MAT mat - When obtaining deform data from a MAT or a Deform In MAT, this is where that MAT is specified.

Parameters - Common Page

Blending

Blending is summing the color value of the pixel being drawn and the pixel currently present in the Color-Buffer. Blending is typically used to simulate Transparency.

The blending equation is:

Final Pixel Value = (Source Blend * Source Color) + (Dest Blend * Destination Color)

Blending (Transparency) blending - This toggle enables and disables blending. However see the wiki article Transparency.

Source Color srcblend - This value is multiplied by the color value of the pixel that is being written to the Color-Buffer (also know as the Source Color).

Destination Color destblend - This value is multiplied by the color value of the pixel currently in the Color-Buffer (also known as the Destination Color).

Separate Alpha Function separatealphafunc - This toggle enables and disables separate blending options for the alpha values.

Source Alpha srcblend - This value is multiplied by the alpha value of the pixel that is being written to the Color-Buffer (also know as the Source Alpha).

Destination Alpha destblend - This value is multiplied by the alpha value of the pixel currently in the Color-Buffer (also known as the Destination Alpha).

Depth Test

Depth-Testing is comparing the depth value of the pixel being drawn with the pixel currently in the Frame-Buffer. A pixel that is determined to be in-front of the pixel currently in the Frame-Buffer will be drawn over it. Pixels that are determined to be behind the pixel currently in the Frame-Buffer will not be drawn. Depth-Testing allows geometry in a 3D scene to occlude geometry behind it, and be occluded by geometry in-front of it regardless of the order the geometry was drawn.

For a more detailed description of Depth-Testing, refer to the Depth-Test article.

Depth Test depthtest - Enables and disables the Depth-Test. If the depth-test is disabled, depths values aren't written to the Depth-Buffer.

Depth Test Function depthfunc - The depth value of the pixel being drawn is compared to the depth value currently in the depth-buffer using this function. If the test passes then the pixel is drawn to the Frame-Buffer. If the test fails the pixel is discarded and no changes are made to the Frame-Buffer.

Write Depth Values depthwriting - If Write Depth Values is on, pixels that pass the depth-test will write their depth value to the Depth-Buffer. If this isn't on then no changes will be made to the Depth-Buffer, regardless of if the pixels drawn pass or fail the depth-test.

Alpha Test

Alpha-testing allows you to choose to draw or not draw a pixel based on its alpha value.

Discard Pixels Based On Alpha alphatest - This enables or disables the pixel alpha test.

Keep Pixels with Alpha alphatest - This menu works in conjunction with the Alpha Threshold parameter below in determining which pixels to keep based on their alpha value.

Alpha Threshold alphathreshold - This value is what the pixel's alpha is compared to to determine if the pixel should be drawn. Pixels with alpha greater than the Alpha Threshold will be drawn. Pixels with alpha less than or equal to the Alpha Threshold will not be drawn.

Wire Frame

The wire-frame feature will render the geometry as wire-frame, using the actual primitive type used in the render. What this means is surfaces like Metaballs, NURBs and Beziers will become a wire-frame of the triangles/triangle-strips used to render them (since these types of primitives can't be natively rendered in OpenGL).

Wire Frame wireframe - Enables and disables wire-frame rendering with the option of OpenGL Tesselated or Topology based wireframes.

Line Width wirewidth - This value is the width that the wires will be. This value is in pixels.

Cull Face

The cull face parameter will cull faces from the render output. This can be used as an optimization or sometimes to remove artifacts. See Back-Face Culling for more infomation.

Cull Face cullface - Selects which faces to render.

  • Use Render Setting - use the render settings found in the Render or Render Pass TOP.
  • Neither - do not cull any faces, render everything.
  • Back Faces - cull back faces, render front faces.
  • Front Faces - cull front faces, render back faces.
  • Both Faces - cull both faces, render nothing.

Polygon Depth Offset

This feature pushes the polygons back into space a tiny fraction. This is useful when you are rendering two polygons directly on-top of each other and are experiencing Z-Fighting. Refer to Polygon Depth Offset for more information. This is also an important feature when doing shadows.

Polygon Depth Offset polygonoffset - Turns on the polygon offset feature.

Offset Factor polygonoffsetfactor -

Offset Units polygonoffsetunits -


Related Articles

Texture Sampling Parameters

Character Deformations

Deform Article