Parallax mapping - Revision history

Datiswous: /* Caveats */ typos

2025-02-26T08:37:50Z

Caveats: typos

← Older revision		Revision as of 08:37, 26 February 2025
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	=== Caveats ===		=== Caveats ===

	The edges of parallax-mapped material usually look weird, especially when you ~~more~~ camera around.		The edges of parallax-mapped material usually look weird, especially when you move the camera around.
	You can occlude the edges from the viewer with some other geometry. Or you can create such a heightmap which makes zero displacement on the edges.		You can occlude the edges from the viewer with some other geometry. Or you can create such a heightmap which makes zero displacement on the edges.

	As of now, parallax mapping only works on interactions, it does not affect the ambient stages of a material.		As of now, parallax mapping only works on interactions, it does not affect the ambient stages of a material.

Stgatilov at 21:29, 4 January 2025

2025-01-04T21:29:12Z

← Older revision		Revision as of 21:29, 4 January 2025
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	The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.		The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.
	Increasing softness can also help hide dithering from low shadowSteps.		Increasing softness can also help hide dithering from low shadowSteps.


	=== Caveats ===		=== Caveats ===

Stgatilov at 21:28, 4 January 2025

2025-01-04T21:28:54Z

Stgatilov: /* Shadows */

2025-01-04T21:27:46Z

Shadows

← Older revision		Revision as of 21:27, 4 January 2025
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	This is how many linear iterations are performed when searching for shadow ray intersections:		This is how many linear iterations are performed when searching for shadow ray intersections:

	* shadowSteps {integer} (default = 20)		* shadowSteps {integer} (default = 20)

	As usual, increasing it makes self-shadows more reliable but decreases performance.		As usual, increasing it makes self-shadows more reliable but decreases performance.
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	The following parameters defines how soft self-shadows are:		The following parameters defines how soft self-shadows are:

	* shadowSoftness {expression} (default = ?)		* shadowSoftness {expression} (default = ?)

	The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.		The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.
	Increasing softness can also help hide dithering from low shadowSteps.		Increasing softness can also help hide dithering from low shadowSteps.


	=== Caveats ===		=== Caveats ===

Stgatilov at 21:27, 4 January 2025

2025-01-04T21:27:31Z

← Older revision		Revision as of 21:27, 4 January 2025
Line 88:		Line 88:

	Normally, you should not touch this, but sometimes you might get away with low values without breakage.		Normally, you should not touch this, but sometimes you might get away with low values without breakage.


	===== Shadows =====		===== Shadows =====

Stgatilov: First version

2025-01-04T21:27:11Z

First version

New page

This article describes how to set up a material for parallax mapping, which was added in TDM 2.13.

=== Material ===

The new '''parallax stage''' is a part of an '''interaction group''', i.e. a group of stages which together define the reaction of the surface to the surrounding light sources.
This sample material contains only one interaction group that consists of diffuse, bump, and parallax stages (no specular):

textures/test/test_parallax
{
diffusemap textures/test_parallax/parallax_test2_d
bumpmap textures/test_parallax/parallax_test_local2
{
blend parallaxmap
map textures/test_parallax/parallax_test_height
min -0.2
max 0.0
}
}

Note that both height/parallax map (<tt>parallax_test_height</tt>) and normal/bump map (<tt>parallax_test_local2</tt>) are necessary!
Parallax stage alone only displaces the surface fragments according to the relief, but does not affect lighting in any way.
You need bump stage with matching normal map in order to make lighting behave properly according to the relief.

The <tt>min</tt> and <tt>max</tt> parameters specify how the colors in heightmap are converted into physical displacements.
In this specific case, fragments where heightmap = 1.0 (white) stay on the mesh geometry, while fragments where heightmap = 0.0 (black) are displaced inwards by 1/5 of texture tile length.

It is important to set correct value of (<tt>max</tt> - <tt>min</tt>), otherwise lighting will look incorrect.
Normally, you should get this number from the software when you bake height and normal maps.
And if you decide to change this value afterwards, then you need to rebake the normal map.

=== Amount of displacement ===

These parameters define the amount of displacements for full-black and full-white texels in the heightmap respectively:

* min {expression} (default = -0.1)
* max {expression} (default = 0.0)

Positive value corresponds to displacement along surface normal (outwards), while negative pushes the fragments in the opposite way (inwards).

The numbers specify the amount of displacement in UV space / in relative sense. If you have a quad of unit size which is covered by the texture exactly, then <tt>max = 0.35</tt> will displace full-white texels by 0.35. If the same quad is resized to 800 doom units, then <tt>max = 0.35</tt> will mean displacement by 0.35 * 800 = 280 doom units. So if you stretch the texture, the displacements are magnified proportionally in order to keep the match between heightmap and normalmap.

Generally speaking, the case <tt>max = 0</tt> and <tt>min < 0</tt> is the most useful, because it pushes the fragments inside the wall, which is usually solid and impassable by the player. Sometimes <tt>max > 0</tt> might make more sense, but special case should be taken to ensure the player cannot cross the relief.

These parameters are the most important, and you need to set at least one of them explicitly in most cases.

=== Falling shadows ===

Parallax mapping is a hack, the mesh geometry is still used for many purposes, even inside rendering.
For example, if you let a cubic crate case shadow onto parallax-mapped wall, the shadow edges are still straight lines by default, so the surface relief does not affect the shadows falling onto it.

This flag deforms the shadow falling onto the parallax-mapped surface according to the relief:

* offsetExternalShadows {0 or 1} (default = 0)

However, it has two additional caveats:
# It does not work with stencil shadows.
# It also disables shadows cast by the parallax-mapped surface itself.

=== Grazing angles ===

The parallax algorithm does not work well under grazing viewing angles.
That's why the parallax effect is gradually reduced to zero for low angles.

It is controlled by the parameter:

* grazingAngle {float} (default = 0.3)

The parallax gets flattened under view angles lower than this value in radians.

=== Quality and complexity ===

The engine uses simple Parallax Occlusion Mapping algorithm, which intersects a ray with height map per each fragment. The raycasting algorithm is approximate and can miss intersections sometimes. This usually results in visual artifacts along the silhouette edges of relief, which look like staircases.

===== Displacement =====

These parameters controls how many iterations are performed:

* linearSteps {integer} (default = 20)
* refineSteps {integer} (default = 5)

The first parameter is more important. Increasing it reduces the number of missed intersections, making raycasting more reliable but slower.
The second parameter makes detected intersections more precise, but does not help with missed intersections.

Normally, you should not touch this, but sometimes you might get away with low values without breakage.

===== Shadows =====

The self-shadows of parallax-mapped surface are rendered with special algorithm which involves raycasting again =)
This is how many linear iterations are performed when searching for shadow ray intersections:

* shadowSteps {integer} (default = 20)

As usual, increasing it makes self-shadows more reliable but decreases performance.
If the number of shadow steps gets too low, then penumbra will become dithered, which can be annoying.

Setting shadowSteps = 0 completely disables self-shadows.

The following parameters defines how soft self-shadows are:

* shadowSoftness {expression} (default = ?)

The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.
Increasing softness can also help hide dithering from low shadowSteps.

=== Caveats ===

The edges of parallax-mapped material usually look weird, especially when you more camera around.
You can occlude the edges from the viewer with some other geometry. Or you can create such a heightmap which makes zero displacement on the edges.

As of now, parallax mapping only works on interactions, it does not affect the ambient stages of a material.

← Older revision		Revision as of 21:28, 4 January 2025
Line 35:		Line 35:
	These parameters define the amount of displacements for full-black and full-white texels in the heightmap respectively:		These parameters define the amount of displacements for full-black and full-white texels in the heightmap respectively:

	* min {expression} (default = -0.1)		min {expression} (default = -0.1)
	* max {expression} (default = 0.0)		max {expression} (default = 0.0)

	Positive value corresponds to displacement along surface normal (outwards), while negative pushes the fragments in the opposite way (inwards).		Positive value corresponds to displacement along surface normal (outwards), while negative pushes the fragments in the opposite way (inwards).
Line 54:		Line 54:
	This flag deforms the shadow falling onto the parallax-mapped surface according to the relief:		This flag deforms the shadow falling onto the parallax-mapped surface according to the relief:

	* offsetExternalShadows {0 or 1} (default = 0)		offsetExternalShadows {0 or 1} (default = 0)

	However, it has two additional caveats:		However, it has two additional caveats:
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	It is controlled by the parameter:		It is controlled by the parameter:

	* grazingAngle {float} (default = 0.3)		grazingAngle {float} (default = 0.3)

	The parallax gets flattened under view angles lower than this value in radians.		The parallax gets flattened under view angles lower than this value in radians.
Line 81:		Line 81:
	These parameters controls how many iterations are performed:		These parameters controls how many iterations are performed:

	* linearSteps {integer} (default = 20)		linearSteps {integer} (default = 20)
	* refineSteps {integer} (default = 5)		refineSteps {integer} (default = 5)

	The first parameter is more important. Increasing it reduces the number of missed intersections, making raycasting more reliable but slower.		The first parameter is more important. Increasing it reduces the number of missed intersections, making raycasting more reliable but slower.
Line 94:		Line 94:
	This is how many linear iterations are performed when searching for shadow ray intersections:		This is how many linear iterations are performed when searching for shadow ray intersections:

	* shadowSteps {integer} (default = 20)		shadowSteps {integer} (default = 20)

	As usual, increasing it makes self-shadows more reliable but decreases performance.		As usual, increasing it makes self-shadows more reliable but decreases performance.
Line 103:		Line 103:
	The following parameters defines how soft self-shadows are:		The following parameters defines how soft self-shadows are:

	* shadowSoftness {expression} (default = ?)		shadowSoftness {expression} (default = ?)

	The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.		The default value is computed automatically from other parameters, and is around 0.005 if all the other parameters are at defaults.