Added isocontour shader

[sochowski]

• Created isocontour.frag.glsl that renders points within the range of iso_tolerance from any iso_layers[i], where i is in the range of [0, iso_num_layers)
• Added slider to adjust iso_tolerance
• Added buttons to add and remove isocontour layers, as well as the ability to input up to 32 distinct layers

[matthewturk]

We want to keep the idiom here of always updating changed:

Suggested change

	for i in range(len(self.iso_layers)):
	changed, self.iso_layers[i] = imgui.input_float(
	"Layer " + str(i + 1),
	self.iso_layers[i],
	flags=imgui.INPUT_TEXT_ENTER_RETURNS_TRUE,
	)
	for i in range(len(self.iso_layers)):
	_, self.iso_layers[i] = imgui.input_float(
	"Layer " + str(i + 1),
	self.iso_layers[i],
	flags=imgui.INPUT_TEXT_ENTER_RETURNS_TRUE,
	)
	changed = changed or _

[matthewturk]

What if we instead had an array that we filled, like:

Suggested change

	p._set_uniform(
	"iso_layers",
	np.asarray(self.iso_layers + [0.0] * (32 - len(self.iso_layers))),
	)
	v = np.zeros(32, dtype="float32")
	v[:len(self.iso_layers)] = self.iso_layers
	p._set_uniform(
	"iso_layers",
	v
	)

[matthewturk]

(this will need reformatting)

[matthewturk]

We chatted briefly about this on the call, but this may be workable as a ray_tracing-type fragment shader. Not necessary to change it now, though.

[chrishavlin]

Great work! Left one idea on arranging the "Remove Layer" button in line for each layer.

And I thought some more about how to set isocontour values in raw data values. So at least in the case of the block rendering, the data is normalized when building the data Texture objects (in scene_data.block_collection.BlockCollection._load_textures), so when you send iso_layers to the shader it will expect values in the range 0,1. So what I think we should do is add a _get_sanitized_iso_layers method to SceneComponent. The method of normalizing data might change depending on the scene_data type, so we should just pass through the values in base_component.SceneComponent:

def _get_sanitized_iso_layers(self):
     return self.iso_layers

But then override in child classes. So for scene_components.blocks.BlockRendering we'd want to add something like:

def  _get_sanitized_iso_layers(self):
     # return the sanitized layers

     # pull extrema from `BlockCollection`, these are extrema across all blocks
     data_min = self.data.min_val  
     data_max = self.data.max_val  
     
     # apply the same scaling as in `self.data._load_textures()`
     normalized_isovals = [ (iso_val - data_min) / (data_max - data_min) for iso_val in self.iso_layers]
     return normalized_isovals

And then we'd want to send those normalized iso_layers to the shader program instead of the raw iso_layers values from the user input.

[matthewturk]

I'm trying to figure out how to manage this without a while loop, but I can't quite come up with something. So I suppose, this is OK! :)

[chrishavlin]

I also think this is good for now! But I also agree that there could a way to simplify this... maybe separating the initial table construction from row removal when a button is pushed? Would result in more code but might be conceptually simpler. But ya, I say leave this as is for now.

[chrishavlin]

This version looks good! One small code suggestion to add a comment.

[chrishavlin]

Suggested change

	def _get_sanitized_iso_layers(self):
	def _get_sanitized_iso_layers(self):
	# child scene_component classes override this to normalize layer values if needed

[chrishavlin]

I also think this is good for now! But I also agree that there could a way to simplify this... maybe separating the initial table construction from row removal when a button is pushed? Would result in more code but might be conceptually simpler. But ya, I say leave this as is for now.