1 files changed, 50 insertions, 26 deletions
diff --git a/doc/python_api/examples/gpu.10.py b/doc/python_api/examples/gpu.10.py
index a4db576ecc0..2f255b7127d 100644
--- a/doc/python_api/examples/gpu.10.py
+++ b/doc/python_api/examples/gpu.10.py
@@ -1,41 +1,65 @@
 """
-Rendering the 3D View into a Texture
-------------------------------------
+Custom Shader for dotted 3D Line
+--------------------------------
 
-The scene has to have a camera for this example to work.
-You could also make this independent of a specific camera,
-but Blender does not expose good functions to create view and projection matrices yet.
+In this example the arc length (distance to the first point on the line) is calculated in every vertex.
+Between the vertex and fragment shader that value is automatically interpolated
+for all points that will be visible on the screen.
+In the fragment shader the ``sin`` of the arc length is calculated.
+Based on the result a decision is made on whether the fragment should be drawn or not.
 """
 import bpy
-import bgl
 import gpu
-from gpu_extras.presets import draw_texture_2d
+from random import random
+from mathutils import Vector
+from gpu_extras.batch import batch_for_shader
 
-WIDTH = 512
-HEIGHT = 256
+vertex_shader = '''
+    uniform mat4 u_ViewProjectionMatrix;
 
-offscreen = gpu.types.GPUOffScreen(WIDTH, HEIGHT)
+    in vec3 position;
+    in float arcLength;
 
+    out float v_ArcLength;
 
-def draw():
-    context = bpy.context
-    scene = context.scene
+    void main()
+    {
+        v_ArcLength = arcLength;
+        gl_Position = u_ViewProjectionMatrix * vec4(position, 1.0f);
+    }
+'''
+
+fragment_shader = '''
+    uniform float u_Scale;
+
+    in float v_ArcLength;
 
-    view_matrix = scene.camera.matrix_world.inverted()
+    void main()
+    {
+        if (step(sin(v_ArcLength * u_Scale), 0.5) == 1) discard;
+        gl_FragColor = vec4(1.0);
+    }
+'''
 
-    projection_matrix = scene.camera.calc_matrix_camera(
-        context.evaluated_depsgraph_get(), x=WIDTH, y=HEIGHT)
+coords = [Vector((random(), random(), random())) * 5 for _ in range(5)]
 
-    offscreen.draw_view3d(
-        scene,
-        context.view_layer,
-        context.space_data,
-        context.region,
-        view_matrix,
-        projection_matrix)
+arc_lengths = [0]
+for a, b in zip(coords[:-1], coords[1:]):
+    arc_lengths.append(arc_lengths[-1] + (a - b).length)
 
-    bgl.glDisable(bgl.GL_DEPTH_TEST)
-    draw_texture_2d(offscreen.color_texture, (10, 10), WIDTH, HEIGHT)
+shader = gpu.types.GPUShader(vertex_shader, fragment_shader)
+batch = batch_for_shader(
+    shader, 'LINE_STRIP',
+    {"position": coords, "arcLength": arc_lengths},
+)
+
+
+def draw():
+    shader.bind()
+    matrix = bpy.context.region_data.perspective_matrix
+    shader.uniform_float("u_ViewProjectionMatrix", matrix)
+    shader.uniform_float("u_Scale", 10)
+    batch.draw(shader)
 
 
-bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_PIXEL')
+bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW')