---
tags: Texturing, 2023
---

# VR painting experiment

Blender has a 3d brush. This brush is used for sculpting and is planned to be used for texturing. When sculpting or painting a brush operation is performed. This operation transfers 2d mouse cursor to a 3d position. When using XR input devices we should be able to skip this transformation and use the 3d position/direction to cast the location of the brush to the object.

##

namespace blender::dna {
    class wmWindowManager {
    }
    
    class wmXrData {
    }
    
    class wmXrRuntimeData {
    }
    
    class XrActionMap {
    }
    class XrActionMapItem {
        +op: char[MAX_NAME]
        +op_properties: IDProperty
    }
    
    wmWindowManager -> wmXrData: xr
    wmXrData->wmXrRuntimeData: runtime
    wmXrRuntimeData--> XrActionMap: actionmaps
    XrActionMapItem <- XrActionMap: items
}

SCULPT_OT_brush_stoke will have a brush_object pointer property. When this is set in stead of the mouse cursor the location and transformation of the `brush_object` will be used to cast a ray onto the sculpt object.

`over_mesh` already has a `wmOperator` that could be used to read the `brush_object`.
`SCULPT_stroke_get_location` / `SCULPT_raycast_init` requires the sculpt object as well. `SCULPT_raycast_init` will be splitted into mouse cursor/brush_object.

Inside the XrActionMap we want to start the SCULPT_OT_brush_stroke operator with a brush_object that will follow the XrController.

:::info
- The mapping between the Xr Controller and the brush_object still needs to be looked into.
- Check into the scene inspection add-on and API documentation how to do this.
:::

:::info
- Internally mouse position is used to identify movement. Somehow we have to do similar tricks to identify movement. (`initial_mouse`). Detection of movement is done inside `paint_stroke`.
- We might want to abstract this away and support mouse input class and object input class.
:::

package blender {
    class SculptSession {
        
    }
    class StrokeCache {
        
    }
    class Object {}
    
    SculptSession->StrokeCache: cache
    StrokeCache->Object: brush_object
}

package blender::sculpt {
    class ScultRaycaster {
        mouse: float[2]
        object: Object
        
    }
    class SculptRay {
        position: float3
        direction: float3
        rotation: float
    }
}