Implement basic global tablet pressure curve options.

Grease Pencil already implements support for full-featured
per-brush pressure curves, but it is useful to have some
basic global settings that affect all brushes and tools.

This adds two simple options:

- Raw pressure required to achieve full brush intensity.
- Softness control, using a gamma curve internally.

The most important one is the max pressure setting, because it is
critical for ergonomics, but the Linux Wacom driver lacks it.

The softness option internally converts to gamma = 4^-softness.

Reviewers: brecht, campbellbarton

Differential Revision: https://developer.blender.org/D3967

1 files changed, 3 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_userdef_types.h b/source/blender/makesdna/DNA_userdef_types.h
index 6ae6eaed1c6..c9d16351635 100644
--- a/source/blender/makesdna/DNA_userdef_types.h
+++ b/source/blender/makesdna/DNA_userdef_types.h
@@ -618,6 +618,9 @@ typedef struct UserDef {
 	short anisotropic_filter;
 	short use_16bit_textures, use_gpu_mipmap;
 
+	float pressure_threshold_max; /* raw tablet pressure that maps to 100% */
+	float pressure_softness;      /* curve non-linearity parameter */
+
 	float ndof_sensitivity;	/* overall sensitivity of 3D mouse */
 	float ndof_orbit_sensitivity;
 	float ndof_deadzone; /* deadzone of 3D mouse */