Render Pick DAT
The Render Pick DAT lets you get information about the 3D surface at any pixel of any 3D render, allowing you to implement multi-touch on a 3D rendered scene. It samples a rendering (from a Render TOP or a Render Pass TOP) and returns 3D information from the geometry at the specified pick locations.
You feed it a DAT with minimum three columns:
v. A Multi Touch In DAT is usually connected to the Render Pick DAT, where the Multi Touch In DAT points to a container that is displaying the output of the Render TOP.
You can pick from multiple cameras simultaneously. You can specify a
camera which allows the pick to occur from the point of a view other than the first camera listed in the Render TOP. The value in the column can either be a path (relative to the Render Pick DAT, or absolute) to a Camera COMP, or it can be an integer index, started at 0. If it's an index it will select the camera to use if there are multiple cameras listed in the Render TOP, or if there are cameras listed in the 'Custom Pick Camera(s)' parameter. This is useful for various Multi-Camera Rendering setups, and cases such as VR where your picking isn't coming from the point of view of your eye cameras, but instead hand controllers.
The pick location is a u,v (horizontal, vertical) coordinate placed in the table that you connect to the Render Pick DAT input. Each row of the input table represents one pick point to be sampled, except for the first row which contains column headings
v (plus any other unused columns you want). The
v columns are what you would get from a Panel CHOP. The u and v values goes 0 to 1 left to right and bottom to top, no matter what the aspect ratio of the render is.
When Strategy is Always, that u,v location is always sampled and the results are displayed in the corresponding row in the Render Pick DAT output.
The output table will show the path of the geometry that was picked, its position (in a choice of reference frames), surface normal (excluding bump mapping), distance from camera, texture UV coordinate, color, alpha and instance id. It properly picks surfaces with deforming vertices.
There are some examples here:
See also the single-sample Render Pick CHOP.
Parameters - Render Pick Page
strategy - ⊞ - Decides when to update values based on pick interactions.
- While Select
select- Continuously updates values when being selected/picked.
- Hold First Picked
holdfirst- Holds the values first returned when geometry picked.
- Hold Last Picked
holdlast- Holds the values last returned when geometry picked. This differs from the Continuous strategy in that it will hold the last values picked on geometry if the pick starts sampling empty space (no geometry in that part of the scene). Alternatively, using the Continuous strategy the values will be cleared to zero if the pick starts sampling empty space.
always- Continuously updates values at the location picked.
Clear Previous Pick on New Pick
clearprev - This parameter is only enabled when the Strategy is set to Hold Last Picked. When this is on, starting a new pick on empty space will clear the values. When off, the last values will be held if the pick starts on empty space.
responsetime - ⊞ - Determines when the values are updated.
- Next Cook (Faster)
nextcook- The values are captured on the current frame and updated next frame. Results are from the previous frame, but much faster cook times.
- This Cook (Slower)
thiscook- The values are captured and updated in the current frame.
pickradius - Controls the radius of the search area for the pick. If nothing is found at the pick's center it will keep searching for geometry in the search area defined by the Pick Radius.
Pick Radial Step
pickradstep - Used to reduce the searching within the search area. The search area is sampled at locations that correspond to 'spokes' outwards from the center pick point.
Pick Circular Step
pickcirstep - Used to reduce the searching within the search area. The search area is sampled at locations that correspond to 'rings' outwards from the center pick point.
rendertop - Specifies which scene to pick on, and which camera to pick from. By default the first camera listed in the Render TOP will be used for picking. Another camera can be specified with the 'Custom Pick Camera(s)' parameter, and multiple different cameras can be selected using the
camera input column.
Custom Pick Camera(s)
custompickcameras - Picking can be done from the viewport of custom camera(s) by specifying one or more Camera COMP here. If this parameter is blank the cameras from the Render TOP are used. To pick from the viewpoint of multiple different cameras, a
camera column must be specified in the input DAT.
Allow Multi-Camera Rendering
allowmulticamera - Multi-Camera Rendering is a faster way to render multiple passes at the same time, and is thus a speed improvement for doing many picks at the same time. This feature may not work correctly for some older GLSL MATs made in 088 though, so this parameter allows forcing off this speed improvement if necessary. Generally it should be left on though.
Include Non-Pickable Objects
includenonpickable - Includes the non-pickable objects in the picking algorithm such that non-pickable objects may occlude pickable objects. For example, if there is only one pickable object in the scene with lots of additional non-pickable geometry is present, turning this parameter on will prevent the pickable object from being selected if it is behind a non-pickage object (occluded by the non-pickage object).
Merge Input DAT
mergeinputdat - Appends input table to the Render Pick DATs columns.
activatecallbacks - Enables Callback DAT for each pick event.
callbacks - Path to a DAT containing callbacks for pick event received.
Parameters - Options Page
position - ⊞ - Returns the position of the point picked on the geometry. Columns tx, ty, tz.
no- Do not return position values.
- In SOP Space
sopspace- Return position of point picked in SOP transform space.
- In World Space
worldspace- Return position of point picked in world transform space.
- In Camera Space
cameraspace- Return position of point picked in camera transform space.
- Relative to Object
relativetoobj- Return position of point picked relative to object specified in Reference Object parameter.
normal - ⊞ - Returns the normals of the point picked on the geometry. Columns nx, ny, nz.
no- Do not return normal values.
- In SOP Space
sopspace- Return normals of point picked in SOP transform space.
- In World Space
worldspace- Return normals of point picked in world transform space.
- In Camera Space
cameraspace- Return normals of point picked in camera transform space.
- Relative to Object
relativetoobj- Return normals of point picked relative to object specified in Reference Object parameter.
referenceobj - Object used when fetching position or normals Relative to Object.
Fetch Point Color
color - Returns the point color of the point picked on the geometry. Columns cr, cg, cb, ca.
Fetch Texture UV
uv - Returns the texture coordinates of the point picked on the geometry. Columns mapu, mapv, mapw.
depth - Returns the depth of the point picked on the geometry. This value a non-linear ratio of the point's position between the near and far planes of the Depth Buffer. Column is depth.
Fetch Instance ID
instanceid - Returns the Instance ID of the object. This will always be 0 if instancing is off. Column is instance.
Custom Attrib 1
customattrib1 - Specify which custom attributes to return from the object.
Custom Attrib 1 Type
customattrib1type - The type of attribute is selected from this menu.
Custom Attrib 2
customattrib2 - Specify which custom attributes to return from the object.
Custom Attrib 2 Type
customattrib2type - The type of attribute is selected from this menu.
Custom Attrib 3
customattrib3 - Specify which custom attributes to return from the object.
Custom Attrib 3 Type
customattrib3type - The type of attribute is selected from this menu.
Custom Attrib 4
customattrib4 - Specify which custom attributes to return from the object.
Custom Attrib 4 Type
customattrib4type - The type of attribute is selected from this menu.
Parameters - Common Page
language - ⊞ - Select how the DAT decides which script language to operate on.
input- The DAT uses the inputs script language.
node- The DAT uses it's own script language.
extension - ⊞ - Select the file extension this DAT should expose to external editors.
dat- various common file extensions.
- From Language
language- pick extension from DATs script language.
- Custom Extension
custom- Specify a custom extension.
customext - Specifiy the custom extension.
wordwrap - ⊞ - Enable Word Wrap for Node Display.
input- The DAT uses the inputs setting.
on- Turn on Word Wrap.
off- Turn off Word Wrap.
- Input 0: -
Info CHOP Channels
Extra Information for the Render Pick DAT can be accessed via an Info CHOP.
Common DAT Info Channels
- num_rows - Number of rows in this DAT.
- num_cols - Number of columns in this DAT.
Common Operator Info Channels
- total_cooks - Number of times the operator has cooked since the process started.
- cook_time - Duration of the last cook in milliseconds.
- cook_frame - Frame number when this operator was last cooked relative to the component timeline.
- cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.
- cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.
- cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.
- cooked_this_frame - 1 if operator was cooked this frame.
- warnings - Number of warnings in this operator if any.
- errors - Number of errors in this operator if any.