Render TOP

Summary

The Render TOP is used to render all 3D scenes in TouchDesigner. You need to give it a Camera object and a Geometry object as a minimum.

The Geometry object needs to have a Material assigned to it. Materials can be pre-packaged ones like the Phong material, or they can be OpenGL GLSL shaders. All textures and bump maps in Touch materials are TOPs, i.e. files must be read in via Movie In TOPs.

Rendering in TouchDesigner ties in nicely with compositing via the Render TOP and all other TOPs.

The Render TOP renders in many RGBA and single-channel formats, in 8-bit fixed-point up to to 32-bit floating point per pixel component.

It can render transparent surfaces correctly using Multi-Pass Depth Peeling. See below: Order Independent Transparency.

See also Rendering and all the articles in the Rendering Category.

Parameters - Render Page

Camera /camera - Specifies which Camera to look through when rendering the scene.

Geometry /object - Specifies which Geometry will be included in the rendered scene.

Lights /lights - Specifies which Lights will be used to render the scene.

Anti-Alias /antialias - Sets the level of anti-aliasing in the scene. Setting this to higher values uses more graphics memory.

Render Cube Map /cubemap - Renders 6 views as needed for reflection maps in the Phong Material. See also the Cube Map TOP.

Parameters - Advanced Page

Render /render - Enables rendering; 1 = on, 0 = off.

Dither /dither - Dithers the rendering to help deal with banding and other artifacts created by precision limitations of 8-bit displays.

Color Output Needed /coloroutputneeded - This is an optimization if you don't actually need the color result from this pass. Turning this off avoids a copy from the offscreen render buffer to the TOP's texture. When anti-aliasing is enabled, turning this off will also avoid 'resolving' the anti-aliasing.

Draw Depth Only /drawdepthonly - This will cause the render to only draw depth values to the depth buffer. No color values will be created. To make use of the depth buffer, use the Depth TOP.

Alpha-to-Coverage /alphatocoverage - This is a feature that allows you to control how the anti-alias is resolved by using the pixel's alpha value. Say the anti-alias setting is set to 4x. This means that for each final pixel color, it will blend the color values of 4 pixels from the anti-alias buffer. When Alpha-to-Coverage is enabled, the alpha value controls how many pixel samples will be used to create the final pixel value. If your alpha value is 0.75, then 3 of the 4 pixels will be used. If it's 0.5 then 2 of the 4 pixels will be used.

Polygon Depth Offset /polygonoffset - This feature pushes the polygons back into space a tiny fraction. This is useful when you are rendering two polygons directly ontop 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 Offset Factor /polygonoffsetfactor -

Polygon Offset Units /polygonoffsetunits -

Cull Face /cullface - Front Faces, Back Faces, Both Faces, Neither. Will cause the render to avoid rendering certain polygon faces depending on their orientation to the camera. Refer to Back-Face Culling for more information.

# of Color Buffers /numcolorbufs - Any shader you write can output to more than one RGBA buffer at a time. Instead of writting to gl_FragColor in your shader, you write to gl_FragData[i] where i is the color buffer index you want to write the value to.

Depth Buffer Format /depthformat - Use either a 24-bit Fixed-Point or 32-bit Floating-Point depth buffer (single channel image).

Linear Camera-Space Depth /lineardepth - This parameter is enabled when the Depth Buffer Format above is set to 32-bit Floating-Point. This will feed the Depth TOP with linear camera-space depth values.

Override Material /overridemat - This allows you to specify a material that will be applied to every Geometry that is rendered in the Render TOP. It is useful for pre-processing passes where we are outputting information about the geometry rather then lighting them and outputting RGB.

Order-Independent Transparency /orderindtrans - Helps to render transparent geometry in proper depth order. This eliminates the need to sort the geometry based on distance from camera. This process is multi-pass. For every pixel the closest surface is rendered in the first pass, the second closest surface second, up to the number of passes specified by the Transparency Passes parameter below. Turning this option on will disable some advanced features in the Render TOP, as well as anti-aliasing.

The feature is a pixel-based approach, not object-based. So its performance is not directly related to the number of objects, but rather how they are layered.

It uses a technique called Depth Peeling. First you render the normal frame. On your next render you peel away all of the pixels you saw in the first frame, and reveal the pixels underneath them. The next frame you do the same, peeling away the pixels you could see from the 2nd render. And so on. Once all of the renders are done, you re composite each layer Over the other, starting at the farthest back layer.

If you take a sphere for example, you'll need to do 2 passes, the first one for the front of the sphere, and then 2nd will be the inside of the sphere.

If you have 10 spheres, one behind the other. You'll need 19-20 passes to get the correct image.

If you have 10 spheres, each next to each other across the screen, you'll only need 2 passes.

In reality though you will only need 3-5 passes to get an image that's acceptable. It may not be 100% correct, but it'll look pretty close to correct.

Each pass is a full render, so each pass adds significant overhead.

Transparency Passes /transpasses - Number of passes the renderer will use when Order Independant Transparency is turned on.

Display Overdraw /overdraw - This feature visually shows the overdraw in the scene. Refer to the Early Depth-Test article for more information. In particular the Analyzing Overdraw section.

Overdraw Limit /overdrawlimit - This value quantizes the outputted color value to some # of overdraws. Refer to the Early Depth-Test for more information.

Parameters - GLSL Page

The GLSL parameter page allows passing of TOPs (samplers) and uniforms into GLSL MATs in a global fashion, instead of having to bind them to each and every MAT in the system. This is useful for multi-pass techniques. If a MAT defines a sampler/uniform of the same name, the one in the MAT overrides the one in coming from the Render TOP.

Sampler Name /sampler0 (up to sampler4) - This is the sampler name that the GLSL program will use to sample from this TOP. The samplers need to be declared as the same dimensions as the TOP (sampler2D for a 2D TOP, sampler3D for 3D TOP).

TOP /top0 (up to top4) - This is the TOP that will be referenced by the above sampler name above it.

Exposed by the + Button, texture sampling parameters:

Refer to the Texture Sampling Parameters article for more information on the parameters exposed by pressing the + button. The parameter prefix for each of the parameters is top0 up to top4.

Uniform Name /uniname0 (up to uniname4) - The uniform name, as declared in the shader.

Value /val0v (up to val4v) - The value(s) to give the uniform.

Depending on how the uniform is declared, only some of the values of the 4 available per parameter are passes to the shader. For example, if the uniform is declared as a vec2, then only the first 2 values are passes to the shader, the other 2 are ignored.

Parameters - Common Page

Resolution - quickly change the resolution of the TOP's data.

• Input - uses the input's resolution.
• Eighth, Quarter, Half, 2X, 4X, 8X - multiply the input's resolution by that amount.
• Custom Resolution - enables the Custom Res parameter below, giving direct control over res in the X and Y axis.

Custom Res - enabled only when the Resolution parameter is set to Custom Resolution. Some Generators like Constant and Ramp do not use inputs and only use this field to determine their size. The drop down menu on the right provides some commonly used resolutions.

Use Global Resolution Multiplier - Uses the Global Resolution Multiplier found in Edit>Preferences>TOPs. This multiplies all the TOPs resolutions by the set amount. This is handy when working on computers with different hardware specifications. If a project is designed on a desktop workstation with lots of graphics memory, a user on a laptop with only 64MB VRAM can set the Global Resolution Multiplier to a value of half or quarter so it runs at an acceptable speed. By checking this checkbox on, this TOP is affected by the global multiplier.

Aspect Ratio - sets the image aspect ratio allowing any textures to be viewed in any size. Watch for unexpected results when compositing TOPs with different aspect ratios.

• Input - uses the input's aspect ratio.
• Resolution - uses the aspect of the image's defined resolution (ie 512x256 would be 2:1), whereby each pixel is square.
• Custom Aspect Ratio - lets you explicitly define a custom aspect ratio.

Fill Viewer - determine how the TOP image is displayed in the viewer.

• Input - uses the same Fill Viewer settings as it's input.
• Fill - stretches the image to fit the edges of the viewer.
• Fit Horizontal - stretches image to fit viewer horizontally.
• Fit Vertical - stretches image to fit viewer vertically.
• Fit Best - stretches or squashes image so no part of image is cropped.
• Fit Worst - stretches or squashes image so image fills viewer while constraining it's proportions. This often leads to part of image getting cropped by viewer.
• Native Resolution - displays the native resolution of the image in the viewer.

NOTE: To get an understanding of how TOPs works with images, you will want to set this to Native Resolution as you lay down TOPs when starting out. This will let you see what is actually happening without any automatic viewer resizing.

Viewer Smoothness - This controls pixel filtering in the viewers.

• Nearest Pixel - uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
• Interpolate Pixels - uses linear filtering between pixels. This is how you get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
• Mipmap Pixels - uses mipmapfiltering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail. When the input is 32-bit float format nearest filtering will always be used, regardless of what is selected in the menu.

Pixel Format - format used to store data for each channel in the image (ie. R, G, B, and A). Refer to Pixel Formats for more information.

• Input - uses the input's pixel format.
• 8-bit fixed (RGBA) - uses 8-bit integer values for each channel.
• 16-bit float (RGBA) - uses 16-bits per color channel, 64-bits per pixel.
• 32-bit float (RGBA) - uses 32-bits per color channel, 128-bits per pixels.

• 10-bit RGB, 2-bit Alpha, fixed (RGBA) - uses 10-bits per color channel and 2-bits for alpha, 32-bits total per pixel.
• 16-bit fixed (RGBA) - uses 16-bits per color channel, 64-bits total per pixel.
• 11-bit float (RGB), Positive Values Only - A RGB floating point format that has 11 bits for the Red and Green channels, and 10-bits for the Blue Channel, 32-bits total per pixel (therefore the same memory usage as 8-bit RGBA). The Alpha channel in this format will always be 1. Values can go above one, but can't be negative. ie. the range is [0, infinite).
• 8-bit fixed (R) - has 8-bits for the red channel, 8-bits total per pixel.
• 16-bit fixed (R) - has 16-bits for the red channel, 16-bits total per pixel.
• 16-bit float (R) - has 16-bits for the red channel, 16-bits per pixel.
• 32-bit float (R) - has 32-bits for the red channel, 32-bits per pixel.
• 8-bit fixed (RG) - has 8-bits for the red and green channels, 16-bits total per pixel.
• 16-bit fixed (RG) - has 16-bits for the red and green channels, 32-bits total per pixel.
• 16-bit float (RG) - has 16-bits for the red and green channels, 32-bits per pixel.
• 32-bit float (RG) - has 32-bits for the red and green channels, 64-bits per pixel.
• 8-bit fixed (A) - An Alpha only format that has 8-bits per channel, 8-bits per pixel.
• 16-bit float (A) - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
• 32-bit float (A) - An Alpha only format that has 32-bits per channel, 32-bits per pixel.