Add support for per-shape physics materials #100748

tancop · 2024-12-22T18:57:09Z

Closes godotengine/godot-proposals#7401.

This PR adds:

Methods shape_set_friction, shape_get_friction, shape_set_bounce, shape_get_bounce to PhysicsServer3D
Property physics_material to Shape3D

This is implemented for both Godot and Jolt Physics (using a custom Jolt physics material like one of the official samples).

Example project that uses two different materials on one body: per-shape-materials.zip

tancop · 2024-12-24T09:12:20Z

Fixed the xml method order and added support for concave shapes.

tancop · 2024-12-25T10:14:32Z

Added support for changing materials at runtime. I had to add a new custom shape type JoltCustomMaterialOverrideShape, add a new virtual method on JoltShape3D and change some others to return a mutable JPH::Ref<JPH::Shape> instead of a JPH::ShapeRefC.

tancop · 2024-12-28T09:12:29Z

@AThousandShips I guess this is ready for review. If you see something wrong or confusing let me know

modules/jolt_physics/shapes/jolt_concave_polygon_shape_3d.cpp

modules/jolt_physics/shapes/jolt_height_map_shape_3d.cpp

modules/jolt_physics/shapes/jolt_world_boundary_shape_3d.cpp

modules/jolt_physics/shapes/jolt_custom_decorated_shape.h

See: godotengine/godot#100748

tancop · 2024-12-30T09:49:32Z

@jrouwe thanks! I saw RestoreMaterialState in the docs but thought it was just for deserializing from binary state. You saved 200 lines and a custom shape slot

modules/jolt_physics/shapes/jolt_custom_shape_type.h

modules/jolt_physics/objects/jolt_shaped_object_3d.cpp

tancop · 2024-12-31T17:48:12Z

Renamed JoltShape3D::_set_material to _update_material, it only changes the generated Jolt material not the shape itself

tancop · 2025-01-03T13:07:07Z

Rebased on latest master

tancop · 2025-05-17T10:10:23Z

@mihe thanks for the review just merged all the changes. I see you removed some casts to uint32_t in new JoltBody3D methods, had to add them back because -Wsign-compare is turned on for official builds

tancop · 2025-05-22T17:28:54Z

@mihe this good to go now or you still got questions? just wanna make sure everything clean before it gets merged

mihe

I found a fairly critical issue with the Godot Physics implementation, and some very minor cosmetic remarks in the Jolt implementation.

Outside of these review comments, I must admit that I'm becoming more and more uncomfortable with the API of these two PhysicsServer*D methods:

void body_set_shape_friction_override(RID p_body, int p_shape_idx, bool p_enable, real_t p_friction = 0.0);
void body_set_shape_bounce_override(RID p_body, int p_shape_idx, bool p_enable, real_t p_bounce = 0.0);

I realize it's a bit late to be having this conversation, and that the current design stems from feedback that have been given here already, so I won't push too hard on this, but the whole thing with having p_enable there, and then defaulting the values to 0.0, just so you can pass false without needing to give it a value. It makes for an odd-looking API in my opinion.

Unfortunately I struggle to think of an alternative that wouldn't ideally require a bool to be added for each material state as well, which seems like a hefty price to pay for what is only (subjectively) a better API.

Anyway, I just figured I'd voice my concern at least, in case anyone had any other ideas, or know of other Godot APIs that do something similar already.

modules/godot_physics_2d/godot_body_2d.h

modules/godot_physics_3d/godot_body_3d.h

modules/jolt_physics/objects/jolt_body_3d.cpp

modules/jolt_physics/objects/jolt_body_3d.h

scene/2d/physics/collision_shape_2d.cpp

scene/3d/physics/collision_shape_3d.cpp

scene/2d/physics/collision_shape_2d.cpp

scene/3d/physics/collision_shape_3d.cpp

scene/3d/physics/collision_shape_3d.h

tancop · 2025-05-27T08:08:20Z

@mihe switched this to use shape owner methods can you take a look if i did it right

tancop · 2025-06-01T07:49:07Z

@Calinou looks like mihe doesnt have time to review. is anyone else free right now?

Calinou

Tested again, it works as expected with GodotPhysics3D and Jolt Physics. Code and documentation look good to me.

I suggest having mihe take a final look at the API still, just in case. We can't change what's exposed once it lands in a stable release, so we need to make sure it's rock-solid.

mihe

I did another pass on this and found some bugs with the recent changes, which you'll find in the review comments. I also threw in some more nitpicks while I was at it.

I've also spent some more time thinking about the PhysicsServer*D API, and I think I've arrived at a better API for this:

func body_set_shape_friction_override(body: RID, shape_idx: int, friction: float) -> void
func body_get_shape_friction(body: RID, shape_idx: int) -> float
func body_is_shape_friction_overridden(body: RID, shape_idx: int) -> bool
func body_clear_shape_friction_override(body: RID, shape_idx: int) -> void

This gets rid of NAN from the API completely, by having body_get_shape_friction fall back on the body's friction when there is no override set, while still not burdening implementers with a separate enabled state.

To save us some time, I've gone ahead and made these changes already, and just like before you'll find the changes here (patch here), which also includes fixes for the new review comments.

Like before, if you have no objections to these changes, I can go ahead and push directly to your fork/branch as well. We're only a few days away from the 4.5 feature freeze, and I don't see anything else in this PR that should prevent this from being merged by then.

EDIT: Changes rebased on top of latest push (de20ef0).

mihe · 2025-06-07T11:10:59Z

scene/2d/physics/collision_object_2d.h

+	_FORCE_INLINE_ bool is_area() const { return area; }
+


This isn't needed anymore.

Suggested change

_FORCE_INLINE_ bool is_area() const { return area; }

mihe · 2025-06-07T11:11:13Z

scene/3d/physics/collision_object_3d.h

+	_FORCE_INLINE_ bool is_area() const { return area; }
+


Same feedback as with 2D.

Suggested change

_FORCE_INLINE_ bool is_area() const { return area; }

mihe · 2025-06-07T11:37:40Z

scene/2d/physics/collision_shape_2d.cpp

+	if (shape.is_null()) {
+		return;
+	}
+


This check doesn't make sense anymore.

Suggested change

if (shape.is_null()) {

return;

}

mihe · 2025-06-07T11:38:03Z

scene/3d/physics/collision_shape_3d.cpp

+	if (shape.is_null()) {
+		return;
+	}
+


Same feedback as with 2D.

Suggested change

if (shape.is_null()) {

return;

}

mihe · 2025-06-07T11:45:15Z

scene/2d/physics/collision_shape_2d.cpp

 	return debug_color;
 }

+void CollisionShape2D::set_physics_material(const Ref<PhysicsMaterial> &p_material) {


You're not disconnecting from the changed signal when the physics material is cleared. See CollisionShape2D::set_shape for reference.

mihe · 2025-06-07T11:54:27Z

servers/extensions/physics_server_3d_extension.cpp

+	GDVIRTUAL_BIND(_body_set_shape_bounce_override, "body", "shape_idx", "enable", "bounce");
+	GDVIRTUAL_BIND(_body_set_shape_friction_override, "body", "shape_idx", "enable", "friction");
+
+	GDVIRTUAL_BIND(_body_get_shape_bounce_override, "body", "shape_idx");
+	GDVIRTUAL_BIND(_body_get_shape_friction_override, "body", "shape_idx");


Very nitpicky, but in most other places friction is listed before bounce.

Suggested change

GDVIRTUAL_BIND(_body_set_shape_bounce_override, "body", "shape_idx", "enable", "bounce");

GDVIRTUAL_BIND(_body_set_shape_friction_override, "body", "shape_idx", "enable", "friction");

GDVIRTUAL_BIND(_body_get_shape_bounce_override, "body", "shape_idx");

GDVIRTUAL_BIND(_body_get_shape_friction_override, "body", "shape_idx");

GDVIRTUAL_BIND(_body_set_shape_friction_override, "body", "shape_idx", "enable", "friction");

GDVIRTUAL_BIND(_body_set_shape_bounce_override, "body", "shape_idx", "enable", "bounce");

GDVIRTUAL_BIND(_body_get_shape_friction_override, "body", "shape_idx");

GDVIRTUAL_BIND(_body_get_shape_bounce_override, "body", "shape_idx");

mihe · 2025-06-07T11:54:55Z

servers/physics_server_2d.cpp

+	ClassDB::bind_method(D_METHOD("body_set_shape_bounce_override", "body", "shape_idx", "enable", "bounce"), &PhysicsServer2D::body_set_shape_bounce_override, DEFVAL(0.0));
+	ClassDB::bind_method(D_METHOD("body_set_shape_friction_override", "body", "shape_idx", "enable", "friction"), &PhysicsServer2D::body_set_shape_friction_override, DEFVAL(0.0));
+
+	ClassDB::bind_method(D_METHOD("body_get_shape_bounce_override", "body", "shape_idx"), &PhysicsServer2D::body_get_shape_bounce_override);
+	ClassDB::bind_method(D_METHOD("body_get_shape_friction_override", "body", "shape_idx"), &PhysicsServer2D::body_get_shape_friction_override);


Same nitpick about the ordering here.

Suggested change

ClassDB::bind_method(D_METHOD("body_set_shape_bounce_override", "body", "shape_idx", "enable", "bounce"), &PhysicsServer2D::body_set_shape_bounce_override, DEFVAL(0.0));

ClassDB::bind_method(D_METHOD("body_set_shape_friction_override", "body", "shape_idx", "enable", "friction"), &PhysicsServer2D::body_set_shape_friction_override, DEFVAL(0.0));

ClassDB::bind_method(D_METHOD("body_get_shape_bounce_override", "body", "shape_idx"), &PhysicsServer2D::body_get_shape_bounce_override);

ClassDB::bind_method(D_METHOD("body_get_shape_friction_override", "body", "shape_idx"), &PhysicsServer2D::body_get_shape_friction_override);

ClassDB::bind_method(D_METHOD("body_set_shape_friction_override", "body", "shape_idx", "enable", "friction"), &PhysicsServer2D::body_set_shape_friction_override, DEFVAL(0.0));

ClassDB::bind_method(D_METHOD("body_set_shape_bounce_override", "body", "shape_idx", "enable", "bounce"), &PhysicsServer2D::body_set_shape_bounce_override, DEFVAL(0.0));

ClassDB::bind_method(D_METHOD("body_get_shape_friction_override", "body", "shape_idx"), &PhysicsServer2D::body_get_shape_friction_override);

ClassDB::bind_method(D_METHOD("body_get_shape_bounce_override", "body", "shape_idx"), &PhysicsServer2D::body_get_shape_bounce_override);

mihe · 2025-06-07T12:21:09Z

scene/2d/physics/collision_object_2d.cpp

+	if (sd.material == p_material) {
+		return;
+	}


This is not correct, since it'll keep the same reference even when we change values within the material.

Suggested change

if (sd.material == p_material) {

return;

}

mihe · 2025-06-07T12:21:20Z

scene/3d/physics/collision_object_3d.cpp

+	if (sd.material == p_material) {
+		return;
+	}


Same feedback as with 2D.

Suggested change

if (sd.material == p_material) {

return;

}

mihe · 2025-06-07T17:42:16Z

modules/godot_physics_2d/godot_body_2d.cpp

 #include "godot_area_2d.h"
 #include "godot_body_direct_state_2d.h"
 #include "godot_constraint_2d.h"
+#include "godot_physics_server_2d.h"


This is not needed.

mihe · 2025-06-09T13:51:25Z

As another last-minute decision, I've omitted the body_is_shape_(friction|bounce)_overridden physics server methods from the API that I suggested above, because I struggle to see a use-case for such a query, and it's not something that's needed by the scene nodes anyway.

If anyone needs this in the future it can trivially be added then instead.

So the PhysicsServer*D API would look like this instead, which I'm mostly happy with:

func body_set_shape_friction_override(body: RID, shape_idx: int, friction: float) -> void
func body_clear_shape_friction_override(body: RID, shape_idx: int) -> void
func body_get_shape_friction(body: RID, shape_idx: int) -> float

The branch/patch linked above should have updated accordingly, but here (patch here) it is again if you need it.

EDIT: Changes have rebased on top of latest push (de20ef0).

Xtarsia · 2025-07-10T17:20:42Z

Does this have any chance of working with Heightmap Shapes? (I belive these construct a grid of Quad shapes under the hood, that are tested for in a specific way due to the nature of heightmaps.)

In Terrain3D I would like to be able to send a physics material "ID" for each Quad. Since We have access to an index map that could determine the dominant texture for any given quad, and that texture has other properties associated with it already, linking each texture ID (upto 32) to a physics material, would essentially Let us have paintable physics materials.

mihe · 2025-07-11T10:55:38Z

Does this have any chance of working with Heightmap Shapes? [...] In Terrain3D I would like to be able to send a physics material "ID" for each Quad.

@Xtarsia Not as-is, no. The same goes for individual triangles in ConcavePolygonShape3D. It's technically doable with Jolt, which supports this for both shapes, but it's not immediately clear to me how you'd go about implementing it for Godot Physics.

Either way, we'd need some way of actually assigning material values to groups of faces, both from a UX perspective and from an API perspective, which is likely quite a bit of work, and better suited for a future PR. The texture approach might make some sense for HeightMapShape3D, but I'm not sure it suits ConcavePolygonShape3D as well.

This lets users override bounce and friction for individual collision shapes instead of using the same properties for the whole body.

tancop requested review from a team as code owners December 22, 2024 18:57

AThousandShips added enhancement topic:physics topic:3d labels Dec 22, 2024

tancop force-pushed the add-per-shape-materials branch 3 times, most recently from 6079b03 to 198281e Compare December 23, 2024 15:27

AThousandShips added this to the 4.x milestone Dec 23, 2024

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jrouwe reviewed Dec 29, 2024

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jrouwe added a commit to jrouwe/JoltPhysics that referenced this pull request Dec 29, 2024

Added PlaneShape::GetMaterial/SetMaterial

18bb698

See: godotengine/godot#100748

tancop force-pushed the add-per-shape-materials branch from e72672f to 65418b3 Compare December 30, 2024 09:40

jrouwe reviewed Dec 30, 2024

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tancop force-pushed the add-per-shape-materials branch from 269885f to de20ef0 Compare July 4, 2025 08:21

Add support for per-shape physics materials

2dd8a5b

This lets users override bounce and friction for individual collision shapes instead of using the same properties for the whole body.

tancop force-pushed the add-per-shape-materials branch from f59f57b to 2dd8a5b Compare August 4, 2025 07:03

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Add support for per-shape physics materials #100748

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Add support for per-shape physics materials #100748

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