434e6d8 · ifsrenderer-linux

ifsrenderer-linux commits / 434e6d8

Composite over the viewport, and stop mangling the camera FOV

Two bugs from the first live-viewport pass, both reported from actually using it.

**The 3D viewport went blank.** The tonemap drew an OPAQUE fullscreen quad, so it
painted over the grid, the objects and the gizmos - "normal viewport doesn't work"
is exactly what that looks like. Alpha is now the tonemapped density, so empty
space is transparent and the fractal composites over the scene with ALPHA
blending, restored to NONE afterwards so the viewport's state is left as found.

**The camera FOV was wrong.** `perspective()` unconditionally applied Camera.cs's
`1 + FieldOfView % 179`, which is right for documents authored against it and
wrong for a real focal length: a 50mm lens is 39.60 degrees and the quirk rendered
it as 40.60. The quirk is now opt-out and stays the default, since documents
depend on it; the viewport passes engine_fov_quirk=False and gets the angle it
asked for. Verified round-tripping 35/50/85mm - implied FOV now equals the input
exactly, where before every one was a degree off.

The horizontal angle is the one the kernel wants, because its projection uses
aspect 1 and applies width/height itself.

Verified the shaders still compile and that gpu.state.blend_set exists and
round-trips. Whether the composite reads well over a lit scene is a judgement call
that needs a real viewport.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

434e6d8fa5f68be22ae4da477401721202a20aad

by plankatron <fleeky@gmail.com> · 2026-08-16T23:00:13.000Z

Changed files (2) +27 -10

blender/ifs_render.py +15 -7

…	…	@@ -96,15 +96,22 @@ def look_at(position, target, up) -> list[list[float]]:
96	96	]
97	97
98	98
99		def perspective(fov_degrees: float, aspect: float, near: float) -> list[list[float]]:
	99	def perspective(fov_degrees: float, aspect: float, near: float,
	100	engine_fov_quirk: bool = True) -> list[list[float]]:
100	101	"""
101	102	`Matrix4x4.CreatePerspectiveFieldOfView` with far = +infinity.
102	103
103		The engine passes `1 + FieldOfView % 179` degrees, aspect 1 and near 0.001
104		(Camera.cs:105). At far = inf the third column degenerates to M33 = -1 and
105		M43 = -near.
	104	At far = inf the third column degenerates to M33 = -1 and M43 = -near.
	105
	106	`engine_fov_quirk` reproduces Camera.cs:105, which passes
	107	`1 + FieldOfView % 179` rather than the angle itself. Documents are authored
	108	against that behaviour so it is the default and must stay - but it mangles a
	109	real focal length (a 50mm lens is ~39.6 degrees, which the quirk turns into
	110	40.6), so anything driving the camera from OUTSIDE a document, like the
	111	Blender viewport, passes False and gets the angle it asked for.
106	112	"""
107		fov = math.radians(1.0 + (fov_degrees % 179.0))
	113	fov = math.radians(1.0 + (fov_degrees % 179.0)) if engine_fov_quirk \
	114	else math.radians(fov_degrees)
108	115	y_scale = 1.0 / math.tan(fov * 0.5)
109	116	x_scale = y_scale / aspect
110	117	return [
…	…	@@ -120,7 +127,8 @@ def matmul(a: list[list[float]], b: list[list[float]]) -> list[list[float]]:
120	127	for r in range(4)]
121	128
122	129
123		def view_projection(position, forward, up, fov_degrees=60.0, near=0.001):
	130	def view_projection(position, forward, up, fov_degrees=60.0, near=0.001,
	131	engine_fov_quirk=True):
124	132	"""
125	133	The engine's view-projection, flattened in .NET's row-major memory order.
126	134
…	…	@@ -130,7 +138,7 @@ def view_projection(position, forward, up, fov_degrees=60.0, near=0.001):
130	138	"""
131	139	target = (position[0] - forward[0], position[1] - forward[1], position[2] - forward[2])
132	140	view = look_at(position, target, (-up[0], -up[1], -up[2]))
133		combined = matmul(view, perspective(fov_degrees, 1.0, near))
	141	combined = matmul(view, perspective(fov_degrees, 1.0, near, engine_fov_quirk))
134	142	return tuple(value for row in combined for value in row)
135	143
136	144

blender/ifs_viewport.py +12 -3

…	…	@@ -65,8 +65,12 @@ void main()
65	65	vec4 h = texelFetch(accum_tex, c, 0);
66	66	float peak = max(float(texelFetch(max_tex, ivec2(0, 0), 0).x), 1.0);
67	67	float d = max(h.w, 1e-12);
68		float s = log(1.0 + brightness * h.w / peak) / log(10.0) / d;
69		fragColor = vec4(clamp(h.rgb * s, 0.0, 1.0), 1.0);
	68	// Alpha IS the tonemapped density, so empty space is transparent and the
	69	// fractal COMPOSITES over the viewport - grid, objects and gizmos stay visible.
	70	// An opaque quad here blanks the whole 3D view.
	71	float lum = log(1.0 + brightness * h.w / peak) / log(10.0);
	72	float s = lum / d;
	73	fragColor = vec4(clamp(h.rgb * s, 0.0, 1.0), clamp(lum, 0.0, 1.0));
70	74	}
71	75	"""
72	76
…	…	@@ -239,10 +243,13 @@ class Session:
239	243	eye = world.translation
240	244	forward = -Vector(world.col[2][:3]) # Blender cameras look down -Z
241	245	up = Vector(world.col[1][:3])
	246	# Horizontal FOV from the viewport's focal length against Blender's 36mm
	247	# sensor. The kernel's projection uses aspect 1 and applies width/height
	248	# itself, so the horizontal angle is the one it wants.
242	249	fov = math.degrees(2.0 * math.atan(18.0 / max(lens, 1.0)))
243	250	return ifs_render.view_projection(
244	251	(eye.x, eye.y, eye.z), (forward.x, forward.y, forward.z),
245		(up.x, up.y, up.z), fov_degrees=fov)
	252	(up.x, up.y, up.z), fov_degrees=fov, engine_fov_quirk=False)
246	253
247	254	# ---------------------------------------------------------------------- draw
248	255
…	…	@@ -306,7 +313,9 @@ class Session:
306	313	self.tonemap.uniform_sampler('max_tex', self.maxbuf)
307	314	self.tonemap.uniform_int('out_size', (self.width, self.height))
308	315	self.tonemap.uniform_float('brightness', self.brightness)
	316	gpu.state.blend_set('ALPHA')
309	317	self.batch.draw(self.tonemap)
	318	gpu.state.blend_set('NONE') # leave the viewport's state as we found it
310	319
311	320	self.frames += 1
312	321	# Keep animating: without this the viewport only refines when nudged.