Alfred Posted May 11, 2019 Share Posted May 11, 2019 Just now, AffinityJules said: If you could get high enough then would see the rainbow as a circle. No drink or drugs required! 14 hours ago, R C-R said: I have occasionally seen circular rainbows while looking out aircraft windows, & rainbows in mists created by fountains & garden hoses, but never an upside down one. AffinityJules and lepr 2 Quote Alfred Affinity Designer/Photo/Publisher 2 for Windows • Windows 10 Home/Pro Affinity Designer/Photo/Publisher 2 for iPad • iPadOS 17.4.1 (iPad 7th gen) Link to comment Share on other sites More sharing options...
R C-R Posted May 11, 2019 Share Posted May 11, 2019 58 minutes ago, AffinityJules said: If you could get high enough then would see the rainbow as a circle. If you get high enough, you might see paisley or other weird patterns in rainbows ... even when there are no rainbows to be seen. Quote All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7 Affinity Photo 1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7 Link to comment Share on other sites More sharing options...
John Rostron Posted May 11, 2019 Share Posted May 11, 2019 18 hours ago, DesignT said: Sorry I disagree rainbow arc is almost of the time a not complete arc An arc is defined as part of a circle, which is just what you see most of the time with a rainbow. If you wish to emulate a natural rainbow, then it should be an arc of a perfect circle. If you want to be even more natural then you should include the shading described above. John R C-R 1 Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
John Rostron Posted May 11, 2019 Share Posted May 11, 2019 16 hours ago, R C-R said: I have occasionally seen circular rainbows while looking out aircraft windows, & rainbows in mists created by fountains & garden hoses, but never an upside down one. You would only get a complete rainbow when the sun was lower in the sky than your viewpoint. So an aircraft would be the ideal location. If there was less moisture in the air at higher altitudes, then you could get a true up-side-down rainbow (as opposed to the circumzenithal one. John Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
R C-R Posted May 11, 2019 Share Posted May 11, 2019 34 minutes ago, John Rostron said: An arc is defined as part of a circle, which is just what you see most of the time with a rainbow. If you wish to emulate a natural rainbow, then it should be an arc of a perfect circle. If you want to be even more natural then you should include the shading described above. You also might need to use masking to emulate how rainbows in nature appear behind objects in the foreground & middle ground, like in the Wikipedia article examples where the rainbow seems to end behind the trees. Quote All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7 Affinity Photo 1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7 Link to comment Share on other sites More sharing options...
DesignT Posted May 11, 2019 Author Share Posted May 11, 2019 8 hours ago, Alfred said: When is a rainbow ever not a complete arc?? Complete arc is in my opinion an arc that will touch the earth on both sides the other arcs are still arcs but don´t touch the earth. Quote MacBook Pro Retina 15" - macOS High Sierra version 10.14.4 Affinity Designer 1.6.1 & 1.71 + Affinity Photo1.6.7 & 1.7.1 + Affinity Publisher 1.71 Link to comment Share on other sites More sharing options...
DesignT Posted May 11, 2019 Author Share Posted May 11, 2019 Well the conversation about rainbows goes well but I do not see any help to get the effect that I need. Can you give me some tips about how can I get this effect ? Instead of be over the background image, I will need to be a solid layer but the layer is cut (mask) in the area where we have the rainbow arc (ellipse) like if we see the the rainbow thru a arc mask. I don´t want that the rainbow overlays the other layer I need the rainbow goes behind the foreground and pass thru an arc cut. It´s enough to give me an Ideia of the technic that I should to get this effect. Anyone ? Thanks you all Quote MacBook Pro Retina 15" - macOS High Sierra version 10.14.4 Affinity Designer 1.6.1 & 1.71 + Affinity Photo1.6.7 & 1.7.1 + Affinity Publisher 1.71 Link to comment Share on other sites More sharing options...
R C-R Posted May 11, 2019 Share Posted May 11, 2019 42 minutes ago, DesignT said: I don´t want that the rainbow overlays the other layer I need the rainbow goes behind the foreground and pass thru an arc cut. The rainbow layer should be above the other layer(s) but by adjusting either its layer transparency, layer blend mode, or whatever you can let part of the underlying image show through, just like it would if it was a real rainbow. If the foreground is not on a separate layer, you can use masking on the rainbow layer to hide it where it would otherwise appear on top of the foreground. It might help to study some photos of rainbows, like those in the Wikipedia article. Quote All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7 Affinity Photo 1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7 Link to comment Share on other sites More sharing options...
John Rostron Posted May 12, 2019 Share Posted May 12, 2019 11 hours ago, DesignT said: Complete arc is in my opinion an arc that will touch the earth on both sides the other arcs are still arcs but don´t touch the earth. According to the Wikipedia article on Arcs in Projective Geometry: Quote A k-arc which can not be extended to a larger arc is called a complete arc However, you do not have to use the Projective Geometry definition. Provided you define your term precisely (as you have) then you can then use it as you wish. As Humpty Dumpty said in Through the Looking Glass by Lewis Carroll: Quote "When I use a word, Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master—that's all." Apologies to those who have seen my allusion to Humpty Dumpty before. John Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
John Rostron Posted May 12, 2019 Share Posted May 12, 2019 (edited) I have just read the Wikipedia article on Rainbows, and there is one property of rainbows that has not been mentioned in trying to emulate a 'natural' rainbow: Quote The colour pattern of a rainbow is different from a spectrum, and the colours are less saturated. There is spectral smearing in a rainbow owing to the fact that for any particular wavelength, there is a distribution of exit angles, rather than a single unvarying angle. Having created a rainbow gradient, then you could either apply a little Gaussian Blur or a little desaturation (or both) to get this effect. EDIT: Another feature of a 'natural' rainbow is that it is only a couple of degrees wide. Those re-creations that I have seen are all noticeably wider than this. John Edited May 12, 2019 by John Rostron Update Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
Alfred Posted May 12, 2019 Share Posted May 12, 2019 4 minutes ago, John Rostron said: According to the Wikipedia article on Arcs in Projective Geometry: Quote A k-arc which can not be extended to a larger arc is called a complete arc I think you’re complicating the issue by taking us into projective geometry, John! Here’s what the Arc (geometry) article on Wikipedia has to say: Quote In Euclidean geometry, an arc (symbol: ⌒) is a closed segment of a differentiable curve. A common example in the plane (a two-dimensional manifold), is a segment of a circle called a circular arc. Quote Alfred Affinity Designer/Photo/Publisher 2 for Windows • Windows 10 Home/Pro Affinity Designer/Photo/Publisher 2 for iPad • iPadOS 17.4.1 (iPad 7th gen) Link to comment Share on other sites More sharing options...
John Rostron Posted May 12, 2019 Share Posted May 12, 2019 2 minutes ago, Alfred said: I think you’re complicating the issue by taking us into projective geometry, I gave that source as it did refer to a 'complete arc', which no-where else did. My point being that the term 'complete arc' is essentially one which you can define as you wish, as @DesignT has done. John Alfred 1 Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
R C-R Posted May 12, 2019 Share Posted May 12, 2019 1 minute ago, Alfred said: I think you’re complicating the issue by taking us into projective geometry, John! So ... anybody ever seen a rainbow in nature or a photograph of one that is not a circular arc? I have not, & I am not sure it is even possible. Quote All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7 Affinity Photo 1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7 Link to comment Share on other sites More sharing options...
John Rostron Posted May 12, 2019 Share Posted May 12, 2019 4 minutes ago, R C-R said: So ... anybody ever seen a rainbow in nature or a photograph of one that is not a circular arc? I have not, & I am not sure it is even possible. No it is not. The rainbow is a pure image derived from optical refraction which ensures that it will always be a pure circular arc. John Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
GRH Posted May 12, 2019 Share Posted May 12, 2019 I have seen white rainbows. Quote Mac Pro (Mid 2010) 2.8 GHz Quad-Core Intel Xeon - 16GB RAM - ATI Radeon HD 5770 1024 MB - Asus ProArt 24" 1920 x 1200 iMac 2017 Quad-Core Intel 2.4GHz Cor i5 - 21.5'' Retina 4K - 8Gb RAM - 1TB Fusion drive - Radion Pro 560 4GB - Ventura 13.0.1 Dell Inspiron 15 7000 Series 7559 - i7 6700HQ - 16Mb RAM - 128Gb SSD 1Tb HD - Nvidia GEFORCE GTX 960M 4Gb GDDR5 RAM - 4K Asus N56V i7 3630QM 2.40GHz; 8Mb RAM; 1Tb HD; 64 bit. Nvidia GT 650M 2Gb: 1920 x 1080 - 2nd Monitor: Asus ProArt 24": 1920 x 1200 Link to comment Share on other sites More sharing options...
John Rostron Posted May 12, 2019 Share Posted May 12, 2019 1 hour ago, GRH said: I have seen white rainbows. White rainbows are seen when the light intensity is too low for normal colour vision. See the quoted Wikipedia article for more. John Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
GRH Posted May 19, 2019 Share Posted May 19, 2019 On 5/12/2019 at 9:35 PM, John Rostron said: White rainbows are seen when the light intensity is too low for normal colour vision. See the quoted Wikipedia article for more. John Also known as fogbows, as was the case; brilliant sunshine and slightly foggy. John Rostron 1 Quote Mac Pro (Mid 2010) 2.8 GHz Quad-Core Intel Xeon - 16GB RAM - ATI Radeon HD 5770 1024 MB - Asus ProArt 24" 1920 x 1200 iMac 2017 Quad-Core Intel 2.4GHz Cor i5 - 21.5'' Retina 4K - 8Gb RAM - 1TB Fusion drive - Radion Pro 560 4GB - Ventura 13.0.1 Dell Inspiron 15 7000 Series 7559 - i7 6700HQ - 16Mb RAM - 128Gb SSD 1Tb HD - Nvidia GEFORCE GTX 960M 4Gb GDDR5 RAM - 4K Asus N56V i7 3630QM 2.40GHz; 8Mb RAM; 1Tb HD; 64 bit. Nvidia GT 650M 2Gb: 1920 x 1080 - 2nd Monitor: Asus ProArt 24": 1920 x 1200 Link to comment Share on other sites More sharing options...
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