Texture load in @ti.func

[afiretony]

Hi,
I have a question related with texture load in Taichi.
In example python/taichi/examples/rendering/simple_texture.py, the texture object is declared out of taichi scope, and passed as ti.types.texture type to @ti.kernel function. It seemed that the texture will be converted to taichi.lang._texture.TextureSampler object type.
My question is that how can use texture method like sample_lod or fetch in @ti.func?

[bobcao3]

You need to pass the texture in @ti.template (pass-by-reference)

[afiretony]

Hi @bobcao3 , thanks for answering!
Could you elaborate what do you meant to pass in ti.template?
This is what I tried to do but not works:

texture = ti.Texture(ti.Format.r32f, (n, n, n))

@ti.kernel
def paint(t: ti.f32, n: ti.i32):
    for i, j in pixels:
        uv = ti.Vector([i / res[0], j / res[1], t])
        c = ti.math.vec4(0.0)
        c = sample_tex(texture, uv)
        pixels[i, j] = [c.r, c.r, c.r]

@ti.func
def sample_tex(tex:ti.template(), uv):
    tex.sample_lod(uv, 0.0)

AttributeError: 'Texture' object has no attribute 'sample_lod'

[bobcao3]

You would also need to pass the texture into the kernel. Taichi textures can not be captured through global varaibles

[afiretony]

Hey @bobcao3 thanks, do you mean

@ti.kernel
def paint(t: ti.f32, tex: ti.types.texture(num_dimensions=3), n: ti.i32):
    for i, j in pixels:
        uv = ti.Vector([i / res[0], j / res[1], t])
        c = ti.math.vec4(0.0)
        c = sample_tex(tex, uv)
        pixels[i, j] = [c.r, c.r, c.r]

@ti.func
def sample_tex(tex:ti.template(), uv):
    tex.sample_lod(uv, 0.0)

But still gets error:

Traceback (most recent call last):
File "playground.py", line 93, in
main()
File "playground.py", line 86, in main
paint(t,texture, n)
File "C:\Users\Anaconda3\envs\taichi\lib\site-packages\taichi\lang\kernel_impl.py", line 974, in wrapped
return primal(*args, **kwargs)
File "C:\Users\Anaconda3\envs\taichi\lib\site-packages\taichi\lang\kernel_impl.py", line 901, in call
return self.runtime.compiled_functionskey
File "C:\Users\Anaconda3\envs\taichi\lib\site-packages\taichi\lang\kernel_impl.py", line 826, in func__
raise e from None
File "C:\Users\Anaconda3\envs\taichi\lib\site-packages\taichi\lang\kernel_impl.py", line 823, in func__
t_kernel(launch_ctx)
RuntimeError: [type_factory.cpp:taichi::lang::promoted_type@222] Assertion failure: a->is() && b->is()

[bobcao3]

Hmmmmm. That seems like a bug? Let me check

[ailzhang]

@afiretony sorry for the late reply, this is not a bug since your ti.func is missing a return but we didn't do well in error reporting lol.

This works for me:

@ti.func
def sample_tex(tex: ti.template(), uv):
    return tex.sample_lod(uv, 0.0)

@ti.kernel
def paint(t: ti.f32, pixels: ti.types.ndarray(ndim=2),
          tex: ti.types.texture(num_dimensions=2)):
    for i, j in pixels:
        uv = ti.Vector([i / res[0], j / res[1]])
        warp_uv = uv + ti.Vector(
            [ti.cos(t + uv.x * 5.0),
             ti.sin(t + uv.y * 5.0)]) * 0.1
        c = ti.math.vec4(0.0)
        if uv.x > 0.5:
            # c = tex.sample_lod(warp_uv, 0.0)
            c = sample_tex(tex, warp_uv)
        else:
            c = tex.fetch(ti.cast(warp_uv * 128, ti.i32), 0)
        pixels[i, j] = [c.r, c.r, c.r, 1.0]

Let us know if you have followup questions! We'll try to improve the error message here.

[afiretony]

Thank you @ailzhang for pointing that out! Didn't notice such an obvious mistake here hahaha.