Geometry Nodes: Add Viewport Transform node #118680
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Jacques Lucke
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Reference: blender/blender#118680
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Delete Branch "HooglyBoogly/blender:geometry-nodes-viewport-transform"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
Add a node that outputs the transform of the viewport relative to the
self object's transform. This node can be used to build effects like
billboarding or aligning geometry to the current view. In combination
with the mouse position node in the future it will allow tools like
generating geometry at the mouse click position.
There are two output matrices. The first is the projection matrix
that takes positions in camera space and applies the final perspective
projection. The other is the "view" matrix which contains the location
and rotation of the camera. These are separate because though their
combination is useful, it isn't used like a typical rotation/transform matrix.
Example node group to be used for aligning to camera (billboards):
It might be useful to also add a boolean wheher or not the user is in camera view?
I don't doubt it, but do you have a use case in mind? Maybe it's more generally useful to have a camera object output for those cases.
@blender-bot build
What do you think should be the merging strategy here? With this node but without
Mouse Positionwe are not really in a releasable state.Would be good to have an example of how you intend people to use this.
I think this still has value on its own. Things like billboarding or aligning geometry to the camera which is a relatively common modeling operation could use this. I planned to create a PR for the mouse position node right after this is committed.
Ok, well then maybe add a simple example in the PR description? Currently, it says that the node is not useful as is.
Ah right, sorry. Will do!
Need to merge
mainagain. Also, last time I tried the setup in the image it didn't work. Did you try it yourself? Can you provide a .blend file?Of course :P I misinterpreted the results though, in retrospect it was clearly not working. And I realized that's because the
persmatisn't a proper rotation matrix. We need to output the view and projection matrices separately from this node. For raycasting use cases, they can be combined with a multiply matrix node. For "align to camera" use cases, the view matrix is enough.Sure, attached a simple example.
The example for how to align something to the view seems to work fine for orthographic view or when the object is in the center of the 3D view. I found that this works better in perspective mode, because it actually aligns the matrix to the camera position instead of just to the viewing direction. Unfortunately, this approach does not work so well for orthographic view, because there the camera position is less well defined.
Any thoughts on how to deal with this? Might also be good to expose the camera position for perspective mode directly.
@ -0,0 +13,4 @@static void node_declare(NodeDeclarationBuilder &b){b.add_output<decl::Matrix>("Projection").description("The 3D viewport's perspective projection matrix");perspective or orthographic?
Okay I guess it deals with orthographic projection too. I'll change it to
perspective or orthographic@ -0,0 +24,4 @@return;}const Object &self_object = *params.self_object();const RegionView3D &rv3d = *params.user_data()->call_data->operator_data->rv3d;Node group operators should work even when there is no 3D view.
I'd rather not output redundant information from this node, I think that's more confusing than helpful for this sort of low level building block. I'd expect there to be some way to check if a matrix is orthographic/perspective in the future, then some node group using this can change its behavior based on that.
Would like to see the billboard example more explicitly in the PR description (with screenshot). Other than that, LGTM.