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"""
Test blending and blend equations with float32 framebuffer.
Emulate blend and equation values in python and compare with moderngl.
"""
import pytest
import random
import struct
import moderngl
class TestBlend:
@pytest.fixture(autouse=True)
def ctx_inject(self, ctx):
self.__class__.ctx = ctx
@pytest.fixture(autouse=True)
def vao_inject(self, ctx, color_prog, ndc_quad):
self.__class__.prog = color_prog
self.__class__.vao = ctx.simple_vertex_array(color_prog, ndc_quad, 'in_vert')
@pytest.fixture(scope="class", autouse=True)
def fbo_inject(self, ctx_static):
self.__class__.fbo = ctx_static.framebuffer(color_attachments=[
ctx_static.texture((1, 1), 4, dtype='f4'),
])
def unpack_fbo(self):
return struct.unpack('4f', self.fbo.read(components=4, dtype='f4')[:16])
def cf(self, blend_func, val, src, dst, src_a, dst_a):
"""Calculate factor
Args:
blend_func: The blend func to use
src: source value (single r, g, b, or a)
dest: dest value (single r, g, b, or a)
src_a: alpha value
dst_a: alpha value
"""
result = None
if blend_func == moderngl.ZERO:
result = 0
if blend_func == moderngl.ONE:
result = val
if blend_func == moderngl.SRC_COLOR:
result = val * src
if blend_func == moderngl.ONE_MINUS_SRC_COLOR:
result = val * (1.0 - src)
if blend_func == moderngl.DST_COLOR:
result = val * dst
if blend_func == moderngl.ONE_MINUS_DST_COLOR:
result = val * (1.0 - dst)
if blend_func == moderngl.SRC_ALPHA:
result = val * src_a
if blend_func == moderngl.ONE_MINUS_SRC_ALPHA:
result = val * (1.0 - src_a)
if blend_func == moderngl.DST_ALPHA:
result = val * dst_a
if blend_func == moderngl.ONE_MINUS_DST_ALPHA:
result = val * (1.0 - dst_a)
if result is None:
raise ValueError("Unsupported blend_func")
# Don't clamp here. It needs to happen in the combine
return result
def bleq(self, bsx, bdx, sx, dx, func):
"""Blend equation. Note that MIN and MAX have special behavior.
Args:
bsx: blended source value
bdx: blended dest value
sx: original value from source
dx: original value from dest
"""
if func == moderngl.FUNC_ADD:
return bsx + bdx
elif func == moderngl.FUNC_SUBTRACT:
return bsx - bdx
elif func == moderngl.FUNC_REVERSE_SUBTRACT:
return bdx - bsx
elif func == moderngl.MIN:
return min(sx, dx)
elif func == moderngl.MAX:
return max(sx, dx)
else:
raise ValueError('Unsupported blend equation: {}'.format(func))
def blend_emulate(self, src, dst, blend_func, blend_equation):
"""Emulates blending in python"""
sr = self.cf(blend_func[0], src[0], src[0], dst[0], src[3], dst[3])
sg = self.cf(blend_func[0], src[1], src[1], dst[1], src[3], dst[3])
sb = self.cf(blend_func[0], src[2], src[2], dst[2], src[3], dst[3])
sa = self.cf(blend_func[2], src[3], src[3], dst[3], src[3], dst[3])
dr = self.cf(blend_func[1], dst[0], src[0], dst[0], src[3], dst[3])
dg = self.cf(blend_func[1], dst[1], src[1], dst[1], src[3], dst[3])
db = self.cf(blend_func[1], dst[2], src[2], dst[2], src[3], dst[3])
da = self.cf(blend_func[3], dst[3], src[3], dst[3], src[3], dst[3])
return (
self.bleq(sr, dr, src[0], dst[0], blend_equation[0]),
self.bleq(sg, dg, src[1], dst[1], blend_equation[0]),
self.bleq(sb, db, src[2], dst[2], blend_equation[0]),
self.bleq(sa, da, src[3], dst[3], blend_equation[1]),
)
def blend_moderngl(self, src, dst, blend_func, blend_equation):
"""Performs blending in moderngl.
Args:
src (tuple): The source fragment (r, g, b, a)
dst (tuple): The destination fragment (r, g, b, a)
blend_func (tuple): The blend func
blend_func (tuple): The blend equation
Returns:
The result fragment
"""
self.fbo.use()
self.fbo.clear(red=dst[0], green=dst[1], blue=dst[2], alpha=dst[3])
self.ctx.enable(moderngl.BLEND)
self.prog['color'].value = src
self.ctx.blend_func = blend_func
self.ctx.blend_equation = blend_equation
self.vao.render(mode=moderngl.TRIANGLE_STRIP)
return self.unpack_fbo()
def test_blend_default(self):
src = (0.0, 1.0, 0.0, 0.2)
dst = (1.0, 0.0, 1.0, 0.3)
blend_func = (
moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
)
blend_equation = moderngl.FUNC_ADD, moderngl.FUNC_ADD
a = self.blend_emulate(src, dst, blend_func, blend_equation)
b = self.blend_moderngl(src, dst, blend_func, blend_equation)
assert pytest.approx(a, abs=1.0e-6) == b
def test_blend_separate(self):
src = (0.2, 0.6, 0.1, 0.3)
dst = (0.3, 0.1, 0.4, 0.2)
blend_func = (
moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
moderngl.ONE, moderngl.ONE,
)
blend_equation = moderngl.FUNC_ADD, moderngl.FUNC_ADD
a = self.blend_emulate(src, dst, blend_func, blend_equation)
b = self.blend_moderngl(src, dst, blend_func, blend_equation)
assert pytest.approx(a, abs=1.0e-6) == b
def test_blend_separate_equation(self):
src = (0.2, 0.6, 0.1, 0.3)
dst = (0.3, 0.1, 0.4, 0.2)
blend_func = (
moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
moderngl.ONE, moderngl.ONE,
)
blend_equation = moderngl.FUNC_REVERSE_SUBTRACT, moderngl.MAX
a = self.blend_emulate(src, dst, blend_func, blend_equation)
b = self.blend_moderngl(src, dst, blend_func, blend_equation)
assert pytest.approx(a, abs=1.0e-6) == b
def test_blend_chaos(self):
"""Pick N random colors with random blend modes and equations"""
bf = [
moderngl.ZERO, moderngl.ONE, moderngl.SRC_COLOR, moderngl.ONE_MINUS_SRC_COLOR,
moderngl.DST_COLOR, moderngl.ONE_MINUS_DST_COLOR, moderngl.SRC_ALPHA,
moderngl.ONE_MINUS_SRC_ALPHA, moderngl.DST_ALPHA, moderngl.ONE_MINUS_DST_ALPHA,
]
eq = [
moderngl.FUNC_ADD, moderngl.FUNC_SUBTRACT, moderngl.FUNC_REVERSE_SUBTRACT,
moderngl.MIN, moderngl.MAX,
]
for _ in range(100):
src = tuple([random.uniform(0, 1) for i in range(4)])
dst = tuple([random.uniform(0, 1) for i in range(4)])
blend_func = tuple([random.choice(bf) for i in range(4)])
blend_equation = random.choice(eq), random.choice(eq)
a = self.blend_emulate(src, dst, blend_func, blend_equation)
b = self.blend_moderngl(src, dst, blend_func, blend_equation)
assert pytest.approx(a, abs=1.0e-6) == b
def test_invalid_blend_func(self):
# TypeError: Not iterable
with pytest.raises(TypeError):
self.ctx.blend_func = moderngl.ONE
# Incorrect tuple size
with pytest.raises(moderngl.Error):
self.ctx.blend_func = moderngl.ONE,
# TypeError: "Test" is not an integer
with pytest.raises(moderngl.Error):
self.ctx.blend_func = moderngl.ONE, "Test"
# Incorrect tuple size=3
with pytest.raises(moderngl.Error):
self.ctx.blend_func = moderngl.ONE, moderngl.ONE, moderngl.ONE
# Incorrect tuple size=5
with pytest.raises(moderngl.Error):
self.ctx.blend_func = (
moderngl.ONE,
moderngl.ONE,
moderngl.ONE,
moderngl.ONE,
moderngl.ONE,
)
# Working versions
self.ctx.blend_func = moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA
self.ctx.blend_func = (
moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
)
def test_invalid_blend_equation(self):
with pytest.raises(moderngl.Error):
self.ctx.blend_equation = None
with pytest.raises(moderngl.Error):
self.ctx.blend_equation = moderngl.MAX, moderngl.MAX, moderngl.MAX
self.ctx.blend_equation = moderngl.MAX
self.ctx.blend_equation = moderngl.MAX, moderngl.MAX
def test_get_values(self):
with pytest.raises(NotImplementedError):
self.ctx.blend_func
with pytest.raises(NotImplementedError):
self.ctx.blend_equation
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