How to draw transparent background in webGL on canvas











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-1
down vote

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https://codepen.io/anon/pen/zMRjwv



In that page, I want to draw a transparent background but it's not working when I use gl.clearColor(0, 0, 0, 0).



 const gl = canvas.getContext('webgl', {alpha: false});


Set alpha:false is also can't because 2D context
attributes: alpha: Boolean that indicates if the canvas contains an alpha channel.



If set to false, the browser will knows that the backdrop is always opaque, which can speed up drawing of transparent content and images.WebGL context.



attributes:
alpha: Boolean that indicates if the canvas contains an alpha buffer.









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  • 1




    Tried to make sense of the original question and improve it.
    – Nic3500
    Nov 22 at 3:40






  • 1




    I'm sorry but 1,000 lines of code are not a Minimal, Complete, and Verifiable example
    – Alon Eitan
    Nov 22 at 5:56












  • I'm sorry I just want to draw transparent background or 2d imge in webgl 3D.
    – 包青天
    Nov 22 at 6:02












  • A lot of answers tell me set gl.clearColor(0, 0, 0, 0). const gl = canvas.getContext('webgl', {alpha: false});But that's wrong.
    – 包青天
    Nov 22 at 6:04










  • You can't have a transparent background with alpha:false.. Alpha:false = 100% opaque period.
    – gman
    Nov 22 at 6:05















up vote
-1
down vote

favorite












https://codepen.io/anon/pen/zMRjwv



In that page, I want to draw a transparent background but it's not working when I use gl.clearColor(0, 0, 0, 0).



 const gl = canvas.getContext('webgl', {alpha: false});


Set alpha:false is also can't because 2D context
attributes: alpha: Boolean that indicates if the canvas contains an alpha channel.



If set to false, the browser will knows that the backdrop is always opaque, which can speed up drawing of transparent content and images.WebGL context.



attributes:
alpha: Boolean that indicates if the canvas contains an alpha buffer.









share|improve this question




















  • 1




    Tried to make sense of the original question and improve it.
    – Nic3500
    Nov 22 at 3:40






  • 1




    I'm sorry but 1,000 lines of code are not a Minimal, Complete, and Verifiable example
    – Alon Eitan
    Nov 22 at 5:56












  • I'm sorry I just want to draw transparent background or 2d imge in webgl 3D.
    – 包青天
    Nov 22 at 6:02












  • A lot of answers tell me set gl.clearColor(0, 0, 0, 0). const gl = canvas.getContext('webgl', {alpha: false});But that's wrong.
    – 包青天
    Nov 22 at 6:04










  • You can't have a transparent background with alpha:false.. Alpha:false = 100% opaque period.
    – gman
    Nov 22 at 6:05













up vote
-1
down vote

favorite









up vote
-1
down vote

favorite











https://codepen.io/anon/pen/zMRjwv



In that page, I want to draw a transparent background but it's not working when I use gl.clearColor(0, 0, 0, 0).



 const gl = canvas.getContext('webgl', {alpha: false});


Set alpha:false is also can't because 2D context
attributes: alpha: Boolean that indicates if the canvas contains an alpha channel.



If set to false, the browser will knows that the backdrop is always opaque, which can speed up drawing of transparent content and images.WebGL context.



attributes:
alpha: Boolean that indicates if the canvas contains an alpha buffer.









share|improve this question















https://codepen.io/anon/pen/zMRjwv



In that page, I want to draw a transparent background but it's not working when I use gl.clearColor(0, 0, 0, 0).



 const gl = canvas.getContext('webgl', {alpha: false});


Set alpha:false is also can't because 2D context
attributes: alpha: Boolean that indicates if the canvas contains an alpha channel.



If set to false, the browser will knows that the backdrop is always opaque, which can speed up drawing of transparent content and images.WebGL context.



attributes:
alpha: Boolean that indicates if the canvas contains an alpha buffer.






css webgl shader






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share|improve this question













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share|improve this question








edited Nov 22 at 16:05









Skynet

4,24452640




4,24452640










asked Nov 22 at 2:05









包青天

32




32








  • 1




    Tried to make sense of the original question and improve it.
    – Nic3500
    Nov 22 at 3:40






  • 1




    I'm sorry but 1,000 lines of code are not a Minimal, Complete, and Verifiable example
    – Alon Eitan
    Nov 22 at 5:56












  • I'm sorry I just want to draw transparent background or 2d imge in webgl 3D.
    – 包青天
    Nov 22 at 6:02












  • A lot of answers tell me set gl.clearColor(0, 0, 0, 0). const gl = canvas.getContext('webgl', {alpha: false});But that's wrong.
    – 包青天
    Nov 22 at 6:04










  • You can't have a transparent background with alpha:false.. Alpha:false = 100% opaque period.
    – gman
    Nov 22 at 6:05














  • 1




    Tried to make sense of the original question and improve it.
    – Nic3500
    Nov 22 at 3:40






  • 1




    I'm sorry but 1,000 lines of code are not a Minimal, Complete, and Verifiable example
    – Alon Eitan
    Nov 22 at 5:56












  • I'm sorry I just want to draw transparent background or 2d imge in webgl 3D.
    – 包青天
    Nov 22 at 6:02












  • A lot of answers tell me set gl.clearColor(0, 0, 0, 0). const gl = canvas.getContext('webgl', {alpha: false});But that's wrong.
    – 包青天
    Nov 22 at 6:04










  • You can't have a transparent background with alpha:false.. Alpha:false = 100% opaque period.
    – gman
    Nov 22 at 6:05








1




1




Tried to make sense of the original question and improve it.
– Nic3500
Nov 22 at 3:40




Tried to make sense of the original question and improve it.
– Nic3500
Nov 22 at 3:40




1




1




I'm sorry but 1,000 lines of code are not a Minimal, Complete, and Verifiable example
– Alon Eitan
Nov 22 at 5:56






I'm sorry but 1,000 lines of code are not a Minimal, Complete, and Verifiable example
– Alon Eitan
Nov 22 at 5:56














I'm sorry I just want to draw transparent background or 2d imge in webgl 3D.
– 包青天
Nov 22 at 6:02






I'm sorry I just want to draw transparent background or 2d imge in webgl 3D.
– 包青天
Nov 22 at 6:02














A lot of answers tell me set gl.clearColor(0, 0, 0, 0). const gl = canvas.getContext('webgl', {alpha: false});But that's wrong.
– 包青天
Nov 22 at 6:04




A lot of answers tell me set gl.clearColor(0, 0, 0, 0). const gl = canvas.getContext('webgl', {alpha: false});But that's wrong.
– 包青天
Nov 22 at 6:04












You can't have a transparent background with alpha:false.. Alpha:false = 100% opaque period.
– gman
Nov 22 at 6:05




You can't have a transparent background with alpha:false.. Alpha:false = 100% opaque period.
– gman
Nov 22 at 6:05












1 Answer
1






active

oldest

votes

















up vote
1
down vote



accepted










The issue with the sample you linked to is that the sample itself is not transparent. It draw a background, then it draws sakura petals, then it applies a glow shader to give the petals a glow. This generates an opaque image so setting the canvas alpha to true (or not setting it all) won't make a difference.



To make it transparent comment out the following lines and change the background color



// gl.bindFramebuffer(gl.FRAMEBUFFER, renderSpec.mainRT.frameBuffer);
// gl.viewport(0, 0, renderSpec.mainRT.width, renderSpec.mainRT.height);
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

// renderBackground();
renderPointFlowers();
// renderPostProcess();


You can then possibly adjust the petal brightness changing this line



col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3));


to this for example



col *= mix(1.8, 3.0, pow(abs(coord.x), 0.3));





share|improve this answer























  • Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
    – 包青天
    Nov 22 at 7:30











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1 Answer
1






active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
1
down vote



accepted










The issue with the sample you linked to is that the sample itself is not transparent. It draw a background, then it draws sakura petals, then it applies a glow shader to give the petals a glow. This generates an opaque image so setting the canvas alpha to true (or not setting it all) won't make a difference.



To make it transparent comment out the following lines and change the background color



// gl.bindFramebuffer(gl.FRAMEBUFFER, renderSpec.mainRT.frameBuffer);
// gl.viewport(0, 0, renderSpec.mainRT.width, renderSpec.mainRT.height);
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

// renderBackground();
renderPointFlowers();
// renderPostProcess();


You can then possibly adjust the petal brightness changing this line



col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3));


to this for example



col *= mix(1.8, 3.0, pow(abs(coord.x), 0.3));





share|improve this answer























  • Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
    – 包青天
    Nov 22 at 7:30















up vote
1
down vote



accepted










The issue with the sample you linked to is that the sample itself is not transparent. It draw a background, then it draws sakura petals, then it applies a glow shader to give the petals a glow. This generates an opaque image so setting the canvas alpha to true (or not setting it all) won't make a difference.



To make it transparent comment out the following lines and change the background color



// gl.bindFramebuffer(gl.FRAMEBUFFER, renderSpec.mainRT.frameBuffer);
// gl.viewport(0, 0, renderSpec.mainRT.width, renderSpec.mainRT.height);
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

// renderBackground();
renderPointFlowers();
// renderPostProcess();


You can then possibly adjust the petal brightness changing this line



col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3));


to this for example



col *= mix(1.8, 3.0, pow(abs(coord.x), 0.3));





share|improve this answer























  • Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
    – 包青天
    Nov 22 at 7:30













up vote
1
down vote



accepted







up vote
1
down vote



accepted






The issue with the sample you linked to is that the sample itself is not transparent. It draw a background, then it draws sakura petals, then it applies a glow shader to give the petals a glow. This generates an opaque image so setting the canvas alpha to true (or not setting it all) won't make a difference.



To make it transparent comment out the following lines and change the background color



// gl.bindFramebuffer(gl.FRAMEBUFFER, renderSpec.mainRT.frameBuffer);
// gl.viewport(0, 0, renderSpec.mainRT.width, renderSpec.mainRT.height);
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

// renderBackground();
renderPointFlowers();
// renderPostProcess();


You can then possibly adjust the petal brightness changing this line



col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3));


to this for example



col *= mix(1.8, 3.0, pow(abs(coord.x), 0.3));





share|improve this answer














The issue with the sample you linked to is that the sample itself is not transparent. It draw a background, then it draws sakura petals, then it applies a glow shader to give the petals a glow. This generates an opaque image so setting the canvas alpha to true (or not setting it all) won't make a difference.



To make it transparent comment out the following lines and change the background color



// gl.bindFramebuffer(gl.FRAMEBUFFER, renderSpec.mainRT.frameBuffer);
// gl.viewport(0, 0, renderSpec.mainRT.width, renderSpec.mainRT.height);
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

// renderBackground();
renderPointFlowers();
// renderPostProcess();


You can then possibly adjust the petal brightness changing this line



col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3));


to this for example



col *= mix(1.8, 3.0, pow(abs(coord.x), 0.3));






share|improve this answer














share|improve this answer



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edited Nov 22 at 9:14









Temani Afif

60.9k93572




60.9k93572










answered Nov 22 at 7:22









gman

45.6k17109194




45.6k17109194












  • Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
    – 包青天
    Nov 22 at 7:30


















  • Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
    – 包青天
    Nov 22 at 7:30
















Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
– 包青天
Nov 22 at 7:30




Problem solved.Thank you very much.And apologize for my actions.I asked for an example of nearly a 1000 lines of code.I'm so sorry and grateful.
– 包青天
Nov 22 at 7:30


















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