orient particle to specific axis: Page 5

orient particle to specific axis

DJM

nope i was wrong vector3.right lookat doesnt work, sorry

DJM

vector3.forward lookat seems to work best

xyz

Try with some random vector for up Vector3(13.123, -7.21, 4.923).normalized()

We'll also need to see structure and transformations of nodes in the decal scene. Btw it's hard to tell what's happening in that screenshot. Try to post some runtime screens so we can see what actually happens.

And @DJM, mate, you should really stop saying "doesn't work" or "works best" :) This is computers. It either works as we expect it to, or it displays such and such and such (precisely described) unwanted behavior.

At this point it'd probably be best to send me the project so I can take a look. If you feel comfortable, of course. You can strip off all irrelevant stuff. Just leave the minimum that shows the problem.

cybereality

Yeah, I think the switch to GodotPhysics is a good idea. Bullet is okay, and has been used in some big games (I think GTA IV used it) but honestly I feel like it is pretty bloated, and development fell off a few years ago. It's not really competitive anymore.

xyz

Also the documentation is pretty bad. It basically boils down to reading comments in the code.

DJM

@xyz said: Try with some random vector for up Vector3(13.123, -7.21, 4.923).normalized()

We'll also need to see structure and transformations of nodes in the decal scene. Btw it's hard to tell what's happening in that screenshot. Try to post some runtime screens so we can see what actually happens.

And @DJM, mate, you should really stop saying "doesn't work" or "works best" :) This is computers. It either works as we expect it to, or it displays such and such and such (precisely described) unwanted behavior.

At this point it'd probably be best to send me the project so I can take a look. If you feel comfortable, of course. You can strip off all irrelevant stuff. Just leave the minimum that shows the problem.

ill send u the project , its 1 gig large tho ;)

xyz

There were 3 things:

1) Your particle system must emit in local space. blastoff's Local Coords checkbox must be ON.

2) Fix occasional problem when normal aligns with up axis (happens only with vertical walls in your case). When orienting the decal via look_at() check if normal and up coincide and simply pick another up:

impact.global_transform.origin = p
var up = Vector3.UP
if up.is_equal_approx(n):
	up = Vector3.RIGHT
impact.look_at_from_position(p, p - n, up)
impact.forward = Vector3(0.0, 0.0, 1.0)
impact.cam = maincam

3) And this is the main culprit. Your spatial material assigned to particles had its Billboard Mode set to Particle Billboard. This forced the particle to face the camera, effectively nullifying all the work we did in the particle process shader to orient the particle. So if you set material's Billboard Mode to Dsiabled the particle will retain proper orientation we calculated in the particle shader.

However when you do so you lose frame animation setup. Don't know how to fix this via gui. The quick way it can be fixed is: - keep the Billboard Mode set to Particle Billboarad - convert spatial material to shader material - open the shader source and in vertex() function comment out matrix manipulation lines but keep the frame animation part intact:

void vertex() {
	UV=UV*uv1_scale.xy+uv1_offset.xy;
	//mat4 mat_world = mat4(normalize(CAMERA_MATRIX[0])*length(WORLD_MATRIX[0]),normalize(CAMERA_MATRIX[1])*length(WORLD_MATRIX[0]),normalize(CAMERA_MATRIX[2])*length(WORLD_MATRIX[2]),WORLD_MATRIX[3]);
	//mat_world = mat_world * mat4( vec4(cos(INSTANCE_CUSTOM.x),-sin(INSTANCE_CUSTOM.x), 0.0, 0.0), vec4(sin(INSTANCE_CUSTOM.x), cos(INSTANCE_CUSTOM.x), 0.0, 0.0),vec4(0.0, 0.0, 1.0, 0.0),vec4(0.0, 0.0, 0.0, 1.0));
	//MODELVIEW_MATRIX = INV_CAMERA_MATRIX * mat_world;
	float h_frames = float(particles_anim_h_frames);
	float v_frames = float(particles_anim_v_frames);
	float particle_total_frames = float(particles_anim_h_frames * particles_anim_v_frames);
	float particle_frame = floor(INSTANCE_CUSTOM.z * float(particle_total_frames));
	if (!particles_anim_loop) {
		particle_frame = clamp(particle_frame, 0.0, particle_total_frames - 1.0);
	} else {
		particle_frame = mod(particle_frame, particle_total_frames);
	}	UV /= vec2(h_frames, v_frames);
	UV += vec2(mod(particle_frame, h_frames) / h_frames, floor((particle_frame + 0.5) / h_frames) / v_frames);
}

DJM

tnx!, will try it out

DJM

finally had some time to look at it. now the particle does get stretched based on the hitnormal, wich is what i want. i must be an idiot but the particle doesnt always get alligned with the camera. my first thought is that the hitnormal doesnt get calculated correctly. like u said it gives wrong results on fully flat surfaces(not godot cubes, but trimmeshes i created from imported geo). the rest works fine like expected. is it possible to avoid the "local cords onn" ?because that looks weird on a moving rigidbody

xyz

Well the particle cannot always face the camera because it is constrained to a specific axis. Otherwise it'd be a regular billboard. It tries its best within its degree of freedom to look at the camera. The more the camera look direction is aligned with axis/normal the less visible area of the particle there will be. Nothing you can do about it other than check if that is the case and spawn a regular billboard instead with animation showing the effect in a frontal view. You can even blend between the two depending on the angle of incidence between hit normal and look direction.

Local coords are used precisely so it can follow moving bodies. Perhaps this looks bad with your particular effect. It can easily be adjusted for spawning in global space. Turn the Local Coords off and use forward vector in global space (which is equal to hit normal), and global camera position. in RayCast:

impact.forward = n

in impactnormal:

particlesStretched.process_material.set_shader_param("campos", cam.global_transform.origin)

DJM

tnx for the local space fix there still is a normal calculation vector issue. the impact normal somethimes just takes the last hit normal and not the current correct one. this only happens on my custom (large flat)meshes with static trimmesh colliders, strange issue

xyz

I think it's still just a matter of normal coincidence with the up axis in look_at(). My previous code used is_equal_approx() because it's easier to understand but doesn't account for parallel vectors of opposite direction. The "proper" way to do is via dot product:

var up = Vector3.UP
# if the dot product to close 1 - vectors coincide
# even if they go in opposite directions
if up.dot(n) > .99:
	up = Vector3.RIGHT

DJM

doesnt make a difference. works fine except on my large "concave static body mesh" for the test environment.

xyz

I don't know what's gotten into me lately :) That dot line should be:

if abs(up.dot(n)) > .999:

Concave collider for the room in the test level works fine.

DJM

its strange, the decal spawns correct but if u shoot at a prop and lets say the stretched billboard goes to the side and then shoot at the floor the decal seems to spawn correct but the stretched billboard spawns to the last known position for example to the side if that was the last position.

xyz

Make sure that particle process material has its Local To Scene flag turned on. Otherwise the instances will share shader uniforms.

DJM

@xyz said: Make sure that particle process material has its Local To Scene flag turned on. Otherwise the instances will share shader uniforms.

that did the trick, finally got it working thanks to u. much appreciated

xyz

Finally! I think all of whom participated in this thread deserve a beer. Or whatever their drink of choice is. :) I'll delete your gig and a half from my drive now :)

Btw I still think using a sprite for this is a better choice. But let's not go there at the moment... It also wouldn't be too silly to make a feature request for built-in arbitrary axis particle/sprite billboarding.

DJM

ill drink a "duvel" to u cheers ;) (im belgian) yes a spritesheet might be a better choice. but it would be a nice feature to have in the particle process material. how do u make a feature request ? as u know im rather new here

xyz

Oh? I was in Belgium once, long ago. They fed me Hoegaarden all night. I woke up in a hospital, dressed in that silly paper gown, smiling nurse asking me "too much to drink?" Yeah, lekker. What a nice, overzealous healthcare system you have here... Somebody apparently reported us "bathing" in flowerbeds so ambulance picked us up. I didn't have any recollections of any of it. So cheers! :)

I think requests are done via github https://github.com/godotengine/godot/issues

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