Hi Everyone,
I am trying to model reddish "sandstone" as well as a brick called "Navajo Gold." The red sandstone has uneven, broken "layers" with little bumps on its surface. The Navajo Gold brick varies in color, has tiny holes pocketing its surface, and also may not be flat.
Here is a link to an image of the sandstone:
http://www.lightfoundryllc.com/materials/sandstone.jpg
And a few links to images of the Navajo gold:
http://www.lightfoundryllc.com/materials/ng0.jpg
http://www.lightfoundryllc.com/materials/ng1.jpg
http://www.lightfoundryllc.com/materials/ng2.jpg
http://www.lightfoundryllc.com/materials/ng3.jpg
http://www.lightfoundryllc.com/materials/ngside.jpg
Unfortunately I do not have direct access to the materials, but someone has measured their general reflectance values.
I would like to create a high quality rendering of an interior curved wall made with red sandstone. We are designing skylights for accenting this wall for people outside to see (they would look through a glass curtain wall to see it). Ideally we would like to see little shadows on the surface of the red sandstone due to its uneven layering and some other effects due to its texture.
It would also be nice to have a good rendering of the Navajo Gold brick walls, but this is less of a priority.
Can anyone give any advice for how to model the pattern/textures/etc. for this or have pointers to success stories for these types of materials?
Thanks!
- Dan
···
--
LF logo Daniel C. Glaser, PhD, LEED AP
Principal
Light Foundry, LLC
T: 510.387.8890 | F: 315.410.2617
www.lightfoundryllc.com <http://www.lightfoundryllc.com>
Hi Dan,
as a general rule of thumb, you can modifiers to perturbate the surface (e.g. vary brightness, surface normals) as long as the average of the perturbation is one. In this case you would use your measured reflectance as a base material and apply some fancy structure-modifiers to it.
For the case where you want to perturbate the color, too, it will be more complicated. As far as I understood, you only have the average reflectance, but you do not know the local colors. You may try the same as above, ensuring that the average complies with your measured reflectance, and use colorpict or colorfunc to perturbate the color. But this may leas to strange effects.
Best would be calibrated photographs.
Cheers, Lars.
Hi Dan,
I just got back in and see that I missed this so perhaps my reply is too late to be of use. In any event here are a few thoughts.
If you want to create "high quality" renderings then the best thing to do is to obtain some good photographs of these materials. I know that this can be a challenge as it means that you have to be much more demanding with the client in terms of the information that they need to provide, such as access to decent samples, but it can definitely be worth it. In my experience the best thing to do is to shoot your own photos of good samples and calibrate with the Macbeth Color Checker (or some other mechanism for calibrating reflectance and color). That way you have control over everything. On the other hand if you could perhaps get representative photos from the stone supplier then you could perhaps use these to develop image patterns that can be adjusted to the estimated reflectance information that you do have. Note though if you want the rough surface of the materials to cast shadows depending on how the light is hitting the surface (time of day perhaps), then you will have to use actual geometry, which is going to be a lot more complicated.
Again depending on your rendering/visualization goals and if it just is not possible to get good photos, another approach is to consider what is important to demonstrate given the possible view(s) that you will be showing. For stone masonry materials the first thing that I always consider is how much variation is there from stone to stone. My guess is the sandstone is supposed to have relatively low variation, whereas the brick seems to have quite a high degree of variation. This kind of variation can be accounted for procedurally with a tiling function that varies the brightness and/or color of the tile (stone unit). Another item to consider at this macro level is the relative reflectance of any mortar or joint condition, this again can be treated as part of a procedural tiling function. With these two items accounted for the next thing to try to approximate to some level is variation within a given stone unit. This is where things get a bit more challenging with the materials you are looking at. The sandstone can probably be approximated with some variation of noise functions. The brick though demonstrates some pretty sharp cutoffs in variation and color which I am not sure offhand how I would treat. Just to get the variation it might be worth searching for imagery online and seeing if there is something that you could use to get the variation.
Hope this helps.
Regards,
-Jack de Valpine
···
--
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction
Dan Glaser wrote:
Hi Everyone,
I am trying to model reddish "sandstone" as well as a brick called "Navajo Gold." The red sandstone has uneven, broken "layers" with little bumps on its surface. The Navajo Gold brick varies in color, has tiny holes pocketing its surface, and also may not be flat.
Here is a link to an image of the sandstone:
http://www.lightfoundryllc.com/materials/sandstone.jpg
And a few links to images of the Navajo gold:
http://www.lightfoundryllc.com/materials/ng0.jpg
http://www.lightfoundryllc.com/materials/ng1.jpg
http://www.lightfoundryllc.com/materials/ng2.jpg
http://www.lightfoundryllc.com/materials/ng3.jpg
http://www.lightfoundryllc.com/materials/ngside.jpg
Unfortunately I do not have direct access to the materials, but someone has measured their general reflectance values.
I would like to create a high quality rendering of an interior curved wall made with red sandstone. We are designing skylights for accenting this wall for people outside to see (they would look through a glass curtain wall to see it). Ideally we would like to see little shadows on the surface of the red sandstone due to its uneven layering and some other effects due to its texture.
It would also be nice to have a good rendering of the Navajo Gold brick walls, but this is less of a priority.
Can anyone give any advice for how to model the pattern/textures/etc. for this or have pointers to success stories for these types of materials?
Thanks!
- Dan
--
LF logo Daniel C. Glaser, PhD, LEED AP
Principal
Light Foundry, LLC
T: 510.387.8890 | F: 315.410.2617
www.lightfoundryllc.com <http://www.lightfoundryllc.com>
------------------------------------------------------------------------
_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Dear Jack and Lars,
Thank you very much for the timely modeling advice-- yes, I can see how calibrating the photographs can help with selecting the right color for the stone and brick. Also, thanks for the tips on color variation strategies.
I will let you know what I come up with for the texture. I know its a cross between an art and a science in doing so (e.g. see the "forest" example below)-- just thought maybe someone have studied this material before. On a related note, have there been discussions on having a material database at radiance-online/elsewhere?
On a project where I had to quickly model how a forest would impact the lighting on a facade, I hacked perforate.cal instead of trying to model the actual trees (trunks, branches, needles, yuk).
This was the real scene:
http://www.lightfoundryllc.com/materials/forest/forest.jpg
and this was what was modeled:
http://www.lightfoundryllc.com/materials/forest/model.jpg
and the script I hacked:
http://www.lightfoundryllc.com/materials/forest/forest.cal
Given more time I would have tried to increase the density of the dot pattern near the ground/etc.
- Dan
···
On 4/26/2010 10:05 AM, Jack de Valpine wrote:
Hi Dan,
I just got back in and see that I missed this so perhaps my reply is too late to be of use. In any event here are a few thoughts.
If you want to create "high quality" renderings then the best thing to do is to obtain some good photographs of these materials. I know that this can be a challenge as it means that you have to be much more demanding with the client in terms of the information that they need to provide, such as access to decent samples, but it can definitely be worth it. In my experience the best thing to do is to shoot your own photos of good samples and calibrate with the Macbeth Color Checker (or some other mechanism for calibrating reflectance and color). That way you have control over everything. On the other hand if you could perhaps get representative photos from the stone supplier then you could perhaps use these to develop image patterns that can be adjusted to the estimated reflectance information that you do have. Note though if you want the rough surface of the materials to cast shadows depending on how the light is hitting the surface (time of day perhaps), then you will have to use actual geometry, which is going to be a lot more complicated.
Again depending on your rendering/visualization goals and if it just is not possible to get good photos, another approach is to consider what is important to demonstrate given the possible view(s) that you will be showing. For stone masonry materials the first thing that I always consider is how much variation is there from stone to stone. My guess is the sandstone is supposed to have relatively low variation, whereas the brick seems to have quite a high degree of variation. This kind of variation can be accounted for procedurally with a tiling function that varies the brightness and/or color of the tile (stone unit). Another item to consider at this macro level is the relative reflectance of any mortar or joint condition, this again can be treated as part of a procedural tiling function. With these two items accounted for the next thing to try to approximate to some level is variation within a given stone unit. This is where things get a bit more challenging with the materials you are looking at. The sandstone can probably be approximated with some variation of noise functions. The brick though demonstrates some pretty sharp cutoffs in variation and color which I am not sure offhand how I would treat. Just to get the variation it might be worth searching for imagery online and seeing if there is something that you could use to get the variation.
Hope this helps.
Regards,
-Jack de Valpine
--
LF logo Daniel C. Glaser, PhD, LEED AP
Principal
Light Foundry, LLC
T: 510.387.8890 | F: 315.410.2617
www.lightfoundryllc.com <http://www.lightfoundryllc.com>
Hi Dan,
There have been questions and discussions on a material database. But I think that given the quantity and variety of materials out there this quickly gets out of control. Consider glazing alone with something like Optics5 (a complete software package!) for dealing with this class of materials.
Perhaps another way to consider the forest is by estimating an average transmittance and then just using a trans material. One could even vary this over some vertical dimension.
Best,
-Jack
Dan Glaser wrote:
···
Dear Jack and Lars,
Thank you very much for the timely modeling advice-- yes, I can see how calibrating the photographs can help with selecting the right color for the stone and brick. Also, thanks for the tips on color variation strategies.
I will let you know what I come up with for the texture. I know its a cross between an art and a science in doing so (e.g. see the "forest" example below)-- just thought maybe someone have studied this material before. On a related note, have there been discussions on having a material database at radiance-online/elsewhere? On a project where I had to quickly model how a forest would impact the lighting on a facade, I hacked perforate.cal instead of trying to model the actual trees (trunks, branches, needles, yuk).
This was the real scene:
http://www.lightfoundryllc.com/materials/forest/forest.jpg
and this was what was modeled:
http://www.lightfoundryllc.com/materials/forest/model.jpg
and the script I hacked:
http://www.lightfoundryllc.com/materials/forest/forest.cal
Given more time I would have tried to increase the density of the dot pattern near the ground/etc.
- Dan
On 4/26/2010 10:05 AM, Jack de Valpine wrote:
Hi Dan,
I just got back in and see that I missed this so perhaps my reply is too late to be of use. In any event here are a few thoughts.
If you want to create "high quality" renderings then the best thing to do is to obtain some good photographs of these materials. I know that this can be a challenge as it means that you have to be much more demanding with the client in terms of the information that they need to provide, such as access to decent samples, but it can definitely be worth it. In my experience the best thing to do is to shoot your own photos of good samples and calibrate with the Macbeth Color Checker (or some other mechanism for calibrating reflectance and color). That way you have control over everything. On the other hand if you could perhaps get representative photos from the stone supplier then you could perhaps use these to develop image patterns that can be adjusted to the estimated reflectance information that you do have. Note though if you want the rough surface of the materials to cast shadows depending on how the light is hitting the surface (time of day perhaps), then you will have to use actual geometry, which is going to be a lot more complicated.
Again depending on your rendering/visualization goals and if it just is not possible to get good photos, another approach is to consider what is important to demonstrate given the possible view(s) that you will be showing. For stone masonry materials the first thing that I always consider is how much variation is there from stone to stone. My guess is the sandstone is supposed to have relatively low variation, whereas the brick seems to have quite a high degree of variation. This kind of variation can be accounted for procedurally with a tiling function that varies the brightness and/or color of the tile (stone unit). Another item to consider at this macro level is the relative reflectance of any mortar or joint condition, this again can be treated as part of a procedural tiling function. With these two items accounted for the next thing to try to approximate to some level is variation within a given stone unit. This is where things get a bit more challenging with the materials you are looking at. The sandstone can probably be approximated with some variation of noise functions. The brick though demonstrates some pretty sharp cutoffs in variation and color which I am not sure offhand how I would treat. Just to get the variation it might be worth searching for imagery online and seeing if there is something that you could use to get the variation.
Hope this helps.
Regards,
-Jack de Valpine
--
LF logo Daniel C. Glaser, PhD, LEED AP
Principal
Light Foundry, LLC
T: 510.387.8890 | F: 315.410.2617
www.lightfoundryllc.com <http://www.lightfoundryllc.com>
------------------------------------------------------------------------
_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
It's an ideal "crowdsourcing+research" problem, but it still needs some staffing. Maybe, if I can get some funding...
···
On 2010-04-27 10:44:31 -0700, Jack de Valpine said:
Hi Dan,
There have been questions and discussions on a material database. But I think that given the quantity and variety of materials out there this quickly gets out of control. Consider glazing alone with something like Optics5 (a complete software package!) for dealing with this class of materials.
Perhaps another way to consider the forest is by estimating an average transmittance and then just using a trans material. One could even vary this over some vertical dimension.
Best,
-Jack
Dan Glaser wrote:
Dear Jack and Lars,
Thank you very much for the timely modeling advice-- yes, I can see how calibrating the photographs can help with selecting the right color for the stone and brick. Also, thanks for the tips on color variation strategies.
I will let you know what I come up with for the texture. I know its a cross between an art and a science in doing so (e.g. see the "forest" example below)-- just thought maybe someone have studied this material before. On a related note, have there been discussions on having a material database at radiance-online/elsewhere? On a project where I had to quickly model how a forest would impact the lighting on a facade, I hacked perforate.cal instead of trying to model the actual trees (trunks, branches, needles, yuk).
This was the real scene:
http://www.lightfoundryllc.com/materials/forest/forest.jpg
and this was what was modeled:
http://www.lightfoundryllc.com/materials/forest/model.jpg
and the script I hacked:
http://www.lightfoundryllc.com/materials/forest/forest.cal
Given more time I would have tried to increase the density of the dot pattern near the ground/etc.
- Dan
On 4/26/2010 10:05 AM, Jack de Valpine wrote:
Hi Dan,
I just got back in and see that I missed this so perhaps my reply is too late to be of use. In any event here are a few thoughts.
If you want to create "high quality" renderings then the best thing to do is to obtain some good photographs of these materials. I know that this can be a challenge as it means that you have to be much more demanding with the client in terms of the information that they need to provide, such as access to decent samples, but it can definitely be worth it. In my experience the best thing to do is to shoot your own photos of good samples and calibrate with the Macbeth Color Checker (or some other mechanism for calibrating reflectance and color). That way you have control over everything. On the other hand if you could perhaps get representative photos from the stone supplier then you could perhaps use these to develop image patterns that can be adjusted to the estimated reflectance information that you do have. Note though if you want the rough surface of the materials to cast shadows depending on how the light is hitting the surface (time of day perhaps), then you will have to use actual geometry, which is going to be a lot more complicated.
Again depending on your rendering/visualization goals and if it just is not possible to get good photos, another approach is to consider what is important to demonstrate given the possible view(s) that you will be showing. For stone masonry materials the first thing that I always consider is how much variation is there from stone to stone. My guess is the sandstone is supposed to have relatively low variation, whereas the brick seems to have quite a high degree of variation. This kind of variation can be accounted for procedurally with a tiling function that varies the brightness and/or color of the tile (stone unit). Another item to consider at this macro level is the relative reflectance of any mortar or joint condition, this again can be treated as part of a procedural tiling function. With these two items accounted for the next thing to try to approximate to some level is variation within a given stone unit. This is where things get a bit more challenging with the materials you are looking at. The sandstone can probably be approximated with some variation of noise functions. The brick though demonstrates some pretty sharp cutoffs in variation and color which I am not sure offhand how I would treat. Just to get the variation it might be worth searching for imagery online and seeing if there is something that you could use to get the variation.
Hope this helps.
Regards,
-Jack de Valpine
--
LF logo Daniel C. Glaser, PhD, LEED AP
Principal
Light Foundry, LLC
T: 510.387.8890 | F: 315.410.2617
www.lightfoundryllc.com <http://www.lightfoundryllc.com>
------------------------------------------------------------------------
_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
--
Randolph Fritz
