2D 'POST_VIEW' drawing with gpu.types.GPUShader(vertex_shader, fragment_shader)

Question

I can use gpu.shader.from_builtin("2D_UNIFORM_COLOR") to draw a square to a view (the nodeview), and give it a single color, but I want to use a custom shader. Does anyone have an example of POST_VIEW drawing in 2D using vertex_shader and fragment_shader with gpu.types.GPUShader:

vertex_shader = """
    in vec2 pos;

    void main()
    {
        gl_Position = vec4(pos.x, pos.y, 0.0, 1.0);
    }
"""

fragment_shader = """
    void main()
    {
        gl_FragColor = vec4(1.0, 0.8, 0.8, 1.0);
    }
"""
x = 0
y = 0
w = 150
h = 60
background_coords =  [(x, y), (x + w, y), (w + x, y - h), (x, y - h)]
background_indices = [(0, 1, 2), (0, 2, 3)]


shader = gpu.types.GPUShader(vertex_shader, fragment_shader)
# shader = gpu.shader.from_builtin('2D_UNIFORM_COLOR')
batch = batch_for_shader(shader, 'TRIS', {"pos": background_coords}, indices=background_indices)

shader.bind()
batch.draw(shader)

..which is just about the most basic shader I can come up with.

---

things i learnt:

• to get the basic vertex shader working I needed to remove the call to shader.bind() .
• if your shader gives a message

shader.uniform_float("whatever", ....) not found

it appears to be talking about the constant not being used in the shader, so comment out any shader.uniform_*s that you aren't using.

Answer 1

Unlike 3dview, NodeView does not have:

matrix = context.region_data.perspective_matrix

so in the callback one option is to use gpu.matrix.get_projection_matrix(), it looks something like:

def advanced_grid_xy(context, args):

    geom, config = args
    coords, indices = geom.coords, geom.indices

    matrix = gpu.matrix.get_projection_matrix()
    shader = gpu.types.GPUShader(config.grid.vertex_shader, config.grid.fragment_shader)
    batch = batch_for_shader(shader, 'TRIS', {"pos": coords}, indices=indices)

    shader.bind()
    shader.uniform_float("viewProjectionMatrix", matrix)
    ...
    batch.draw(shader)

that works with this vertex_shader

vertex_shader = '''
    in vec2 pos;
    uniform mat4 viewProjectionMatrix;

    void main()
    {
        gl_Position = viewProjectionMatrix * vec4(pos.x, pos.y, 0.0f, 1.0f);
    }

'''

nice.