Godot 3/4 Particle Shader to Make 'Wandering' Grass With (Or Other Foliage) — Transcript

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1. 0:00good day to you all it's me again
2. 0:01bringing you another episode of making
3. 0:03stuff in godot 4.
4. 0:05today i wanted to present the progress
5. 0:07on my foliage system by using a particle
6. 0:10shader a bit of a disclaimer up front it
7. 0:13is far from finished i'm sure it could
8. 0:15be optimized some more but since we're
9. 0:18working in alpha it's probably too soon
10. 0:20to worry about optimization anyway
11. 0:23i am planning to put it on dropbox if
12. 0:25you want to give it a try but remember
13. 0:27it may be very short-lived given how
14. 0:30things change from one of iteration to
15. 0:33another it simply may not work
16. 0:35anymore by the time you get to try it
17. 0:37out okay so just saying and by the way
18. 0:39in case you do try it out
19. 0:42it would be a display of good manners if
20. 0:44you liked the video and subscribe to the
21. 0:46channel again just saying anyway to the
22. 0:49point um here is something that remotely
23. 0:52resembles a uh a patch of grass and if
24. 0:55you grab it and move it around the scene
25. 0:57it follows the shape of the terrain
26. 1:00the terrain itself has no collision by
27. 1:02the way it's all smoke and mirrors
28. 1:04it's a flat mesh with a vertex shader on
29. 1:06it and you can watch some of my previous
30. 1:09videos to see how it was made now for
31. 1:11demonstration purposes i am going to
32. 1:13replace my grass mesh with a simple box
33. 1:16mesh i'm going to set its height to
34. 1:19something noticeable like 12
35. 1:21and i'm going to reset all these
36. 1:23parameters here on the shader so that we
37. 1:25can start from a clean slate all right
38. 1:29a few ground rules to begin with the
39. 1:31shader is to be used on a gpu particles
40. 1:353d node inside a process material the
41. 1:38amount setting is kind of obvious is how
42. 1:41many instances we're going to have i've
43. 1:44got 10 000
44. 1:45as you can see
45. 1:47lifetime is how quick you want your
46. 1:49particles to respawn if you set it to a
47. 1:51minimum which is equivalent to 10
48. 1:53milliseconds they will respawn in almost
49. 1:55real time as you move the node around
50. 1:57the scene i'm keeping it like this for
51. 1:59demonstration but in an actual game it
52. 2:01will depend on you know how vast your
53. 2:04grass field is going to be and how fast
54. 2:06your player is moving maybe you don't
55. 2:08need to refresh the particles so quickly
56. 2:11it's important to set the explosiveness
57. 2:13to one and randomness to zero otherwise
58. 2:16they will flicker when they refresh let
59. 2:18me show you see what's going on
60. 2:20so if you set explosiveness to maximum
61. 2:22with zero randomness they will be drawn
62. 2:25all at once and that will help you avoid
63. 2:27this issue okay so
64. 2:29let's look at some of the uh fundamental
65. 2:32shader parameters first before we do
66. 2:34anything let's make sure we have our
67. 2:36height map image in this map height map
68. 2:39parameter this of course should be the
69. 2:41same image you're using to deform your
70. 2:44terrain in the vertex shader assuming
71. 2:46you want your grass to snap onto your
72. 2:47terrain of course
73. 2:49optionally you can put in the normal map
74. 2:51of your terrain as well and you will see
75. 2:52what for in just a moment next instance
76. 2:55rose this is crucial because it controls
77. 2:58the emission shape
78. 2:59if you set the particle count to 10 000
79. 3:02like i did
80. 3:03it will just emit a single file row of
81. 3:0610 000 particles starting from the
82. 3:08emitter using this spacing parameter to
83. 3:11space them out but that's not what we
84. 3:12want we don't want single file we want a
85. 3:15patch of grass with the emitter point in
86. 3:17the center of it so we need to tell the
87. 3:20shader how many times we want to divide
88. 3:23this row of particles and this is
89. 3:25exactly what this setting does instance
90. 3:27rows
91. 3:28and the rows will be offset by the same
92. 3:30spacing parameter okay so if you set it
93. 3:32to 100 you're going to get a hundred
94. 3:35rows each with 100 particles totaling to
95. 3:3810 000. so you'll get a nice square uh
96. 3:41patch uh you can see what happens when i
97. 3:43scroll the instance rows value uh our
98. 3:46square patch is kind of morphing into a
99. 3:48rectangle if i got it all the way down
100. 3:50to one it would be a single row uh again
101. 3:53but i want a square so i'm going to
102. 3:54leave it at 100. one important thing to
103. 3:56remember is that
104. 3:58instance rows must be an integer
105. 4:00otherwise if it's a float the particles
106. 4:02will behave erratically when you move
107. 4:04the node around finally terrain
108. 4:06amplitude is the height value that you
109. 4:09have in your terrain vertex shader in my
110. 4:11case it's 100 so i've put 100 here to
111. 4:14make sure that my foliage matches the
112. 4:17shape of the terrain underneath
113. 4:19okay so with the basic settings out of
114. 4:21the way uh let's take a look at some of
115. 4:23the more interesting parameters coverage
116. 4:25altitude is the maximum altitude at
117. 4:28which your foliage will grow it's now
118. 4:31set to 20 but if i dial it in you will
119. 4:34see that the particles that cover the
120. 4:36higher parts the mountains uh begin to
121. 4:38disappear and they're not really
122. 4:39disappearing though they're just they're
123. 4:41still being emitted only way off screen
124. 4:44so we don't have to render them coverage
125. 4:46range is the height range within which
126. 4:48your grass will grow if i set it to
127. 4:50something much smaller like 10 and then
128. 4:53scroll the altitude up and down you'll
129. 4:55see how the particles are moving up and
130. 4:56down the mountain this could be useful
131. 4:58when you want to have like different
132. 5:00types of vegetation at different heights
133. 5:02which happens in nature
134. 5:04slope coverage decides on the extent to
135. 5:07which the grass will grow on slopes so
136. 5:09if i dial it in you'll see that the
137. 5:10particles are starting to disappear from
138. 5:13the areas where the slope is steeper
139. 5:16clamping strength this one is
140. 5:18interesting but before we make sense of
141. 5:20it we need to create a clump map that is
142. 5:23a map that will control where the grass
143. 5:26grows within your patch the easiest way
144. 5:29to go about this one is to create a
145. 5:30noise texture so let's go ahead and do
146. 5:32that i'll create a fast
147. 5:35noise light and i'll give it a type of
148. 5:37ping pong that's what i found works best
149. 5:40for this purpose and i'm going to create
150. 5:42a color ramp to give me some more
151. 5:43control
152. 5:44over the clumping so now if i play
153. 5:47around with the sliders on the color
154. 5:48ramp and noise frequency you'll see that
155. 5:51i'm starting to get some pretty cool
156. 5:52looking uh irregularities so clumping
157. 5:56strength is basically the extent to
158. 5:58which the clump map uh affects the
159. 6:00particles it's like if you are
160. 6:02increasing the contrast on the clamp map
161. 6:04more or less
162. 6:05now we can also orient the particles to
163. 6:08the terrain normal with this checkbox
164. 6:10here
165. 6:11that's what we needed the normal map for
166. 6:14if you remember hopefully you can see
167. 6:15the effect it's not perfect because it's
168. 6:17using an 8-bit normal map image to build
169. 6:20the transform matrix from rgb values of
170. 6:23the pixels if it was a 32-bit normal map
171. 6:25it would probably be more accurate but
172. 6:27still it's kind of okay you can also
173. 6:30adjust the strength of the influence
174. 6:32that the normal map has on the transform
175. 6:34matrix
176. 6:35better yet if you scroll down you'll see
177. 6:38this terrain normal basis parameter with
178. 6:40this you can manipulate the transform
179. 6:43matrix of the normals and you can
180. 6:45achieve some pretty freaky effects with
181. 6:46this like if you wanted to create a
182. 6:49windswept environment for example you
183. 6:50could lay your grass down with the
184. 6:53setting okay moving on instance position
185. 6:55randomize this is going to allow us to
186. 6:57make this rig look more organic as in
187. 7:00more natural you can randomize the
188. 7:02position of the particles we can also
189. 7:05randomize their rotation like so we can
190. 7:07randomize the scale of the particles by
191. 7:10setting a minimum and maximum scale this
192. 7:13alone will randomize their scale but we
193. 7:15can further amplify the randomization
194. 7:17effect with this setting instance scale
195. 7:19randomize okay we can also set the scale
196. 7:22of each of the three axis separately
197. 7:24like if you wanted the instances to be
198. 7:26taller or thicker or whatever and
199. 7:28finally spacing which we discussed in
200. 7:31the beginning controls the scattering of
201. 7:33the individual instances and that my
202. 7:35friends is it so using this shader with
203. 7:38some really simple grass blades that i
204. 7:40made in blender i was able to create
205. 7:43these environments in qatar which
206. 7:45performed quite well while arguably
207. 7:47looking fairly decently in my personal
208. 7:49opinion and that is before any
209. 7:51optimization work has been done on godot
210. 7:534 because remember this is still early
211. 7:56alpha alpha 10 in this particular case
212. 7:58anyway let me know what you think in the
213. 8:00comments
214. 8:01like the video if you enjoyed it find me
215. 8:03on twitter for more frequent updates and
216. 8:05i guess i'll see you in the next episode
217. 8:08peace in the world
218. 8:11[Music]
219. 8:40[Music]
220. 8:45so
221. 8:51[Music]
222. 9:20[Music]
223. 10:27you