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## Bitmap font engine problem

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### #1GuardianX  Members

Posted 20 February 2013 - 09:34 AM

Hello.

I'm trying to create my own text-rendering engine based on Rastertek's tutorial. The steps I did to make it work:

1. Created my own .png file, containing common ASCII symbols divided by spaces. PNG file had not been compressed.

2. Successfully parsed PNG file so that each symbol has it's own texture coordinates and width/height in pixels. The height is the same for each letter and equals to texture height.

3. Created DDS file from PNG font file.

4. Loaded texture from DDS file.

5. Created squares for each letter according to their width/height in pixels and texture coordinates.

6. Created orthogonal projection matrix to project them on the screen within pixel shader without any changes.

Everything seems well, but the result looks bad:

As you can see, the letters look dirty and unprecise. Thats how DDS file looks in DX texture tool for comparison:

Edited by GuardianX, 20 February 2013 - 12:29 PM.

### #2Seabolt  Members

Posted 20 February 2013 - 09:53 AM

What kind of filtering are you using  for your sampler state when you draw it?

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### #3GuardianX  Members

Posted 20 February 2013 - 10:11 AM

Thank you for response. I use this sampler state:

    D3D11_SAMPLER_DESC samplerDesc;
samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
samplerDesc.MipLODBias = 0.0f;
samplerDesc.MaxAnisotropy = 1;
samplerDesc.ComparisonFunc = D3D11_COMPARISON_ALWAYS;
samplerDesc.BorderColor[0] = 0;
samplerDesc.BorderColor[1] = 0;
samplerDesc.BorderColor[2] = 0;
samplerDesc.BorderColor[3] = 0;
samplerDesc.MinLOD = 0;
samplerDesc.MaxLOD = D3D11_FLOAT32_MAX;

mpDevice->CreateSamplerState(&samplerDesc, &mpSamplerState);


### #4Dan Violet Sagmiller  Members

Posted 20 February 2013 - 11:03 AM

Out of curiosity, why don't you use the sprite fonts that are part of XNA.

Anyways, I took a look at more detail.  I thought it might have been a slightly reduced image, but the final image and the original font both show the Capital 'M' at 10 pixels tall.

However, this looks like compression artifacts.  I.e. when it was saved, it may have included a small decompression like PNG/JPG would use.  Or it could be from the loading process.  I haven't used DX font loading of any type, so I'm not sure exactly how it should work, but that really looks like compression artifacts.

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### #5Sporniket  Members

Posted 20 February 2013 - 11:04 AM

Are you sure of your texture coordinate and your vertex coordinates ? I had a similar issue with OpenGl, and I had to correct the texture coordinates. It was years ago though, so I cannot be more accurate.

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### #6GuardianX  Members

Posted 20 February 2013 - 12:28 PM

Thank you for response, guys.

Out of curiosity, why don't you use the sprite fonts that are part of XNA.

Anyways, I took a look at more detail.  I thought it might have been a slightly reduced image, but the final image and the original font both show the Capital 'M' at 10 pixels tall.

However, this looks like compression artifacts.  I.e. when it was saved, it may have included a small decompression like PNG/JPG would use.  Or it could be from the loading process.  I haven't used DX font loading of any type, so I'm not sure exactly how it should work, but that really looks like compression artifacts.

I'm creating my own C++ rendering engine for the sake of learning DX11. Not sure if XNA sprite fonts can be used in such application.

I don't think it is caused by image compressing in my case, since DDS file, generated from image (which I receive uncompressed) looks precise and has no artefacts. However, It is possible that this behavior is caused by loading mechanism. In my engine, I use DDS loader, provided by new Microsoft D3D11 tutorials. I'll create plane with size of the font texture and check if this behavior keeps bubbling up even for sole plane mesh, thanks for pointing that out.

Are you sure of your texture coordinate and your vertex coordinates ? I had a similar issue with OpenGl, and I had to correct the texture coordinates. It was years ago though, so I cannot be more accurate.

Well, I'm absolutely sure about generated vertex coordinates and that I load and set correct texture coordinates from font description file, generated by one of my tools. At first glance, texture coordinates and width of every character, obtained from this tool are legit. The whole mechanism of generating data from PNG file in this tool is just about getting start pixel and end pixel of each symbol and dividing those values by width of the file, so it's pretty clear and simple.

### #7Sporniket  Members

Posted 20 February 2013 - 12:32 PM

So you have startPixel/width and endPixel/width OR startPixel/width and (endPixel + 1)/width ?

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### #8Erik Rufelt  Members

Posted 20 February 2013 - 12:43 PM

If you paste your two images on top of each other and align the letters it's clearly visible that the rendered characters are wider than those in the texture. Perhaps you scale horizontally somewhere. Also, if you manually specify the back-buffer size, double-check that it matches the window client area.

### #9GuardianX  Members

Posted 20 February 2013 - 02:13 PM

So you have startPixel/width and endPixel/width OR startPixel/width and (endPixel + 1)/width ?

If you paste your two images on top of each other and align the letters it's clearly visible that the rendered characters are wider than those in the texture. Perhaps you scale horizontally somewhere. Also, if you manually specify the back-buffer size, double-check that it matches the window client area.

Yeah, I just checked font description generation program and it seems that it was (endPixel+1)/width that caused result letters look wider. Anyway, I fixed it, and result text still looks bad:

Back-buffer's size is okay. By the way, letters on this new screen are 32 pixels tall, so pay no attention to that.

Edited by GuardianX, 20 February 2013 - 02:17 PM.

### #10Dan Violet Sagmiller  Members

Posted 20 February 2013 - 02:14 PM

Out of curiosity, why don't you use the sprite fonts that are part of XNA.

OOPS, a title near this one when I posted had said something about XNA and I confused it slightly with this one, presuming XNA, which as I recall allows the use of DX components.

I'm creating my own C++ rendering engine for the sake of learning DX11. Not sure if XNA sprite fonts can be used in such application.

Yeah, same issue as prior, and I don't think XNA fonts would be usable in DX

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Space Ghost - “Moltar, I have a giant brain that is able to reduce any complex machine into a simple yes or no answer."

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### #11rukiruki  Members

Posted 20 February 2013 - 03:12 PM

For your uv's, can you try x / (width-1), (x+w)/(width-1), y / (height-1), (y+h)/(height-1)?

If you're using endpixel, try endpixel-1 / (with-1)

?

and try with with no filtering in the sampler too.

*edit, erm, the other types of filtering i mean.

Edited by rukiruki, 20 February 2013 - 03:17 PM.

### #12Jason Z  Members

Posted 20 February 2013 - 10:07 PM

I know you are trying to do this as a learning exercise, but have you tried just using the PNG version of the texture instead of the DDS?  It would be worth a shot to see if you can get rid of the compression artifacts as a possible source of error.

If you want to see another reference, MJP added his text renderer to Hieroglyph 3.  Take a look in the SpriteRendererDX11 class, and you will see how he is using GDI to build the glyph texture.  I recall having issues if the source texture was not anti-aliased, and if the origin texture size is slightly off from the end size in the render target.

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### #13Erik Rufelt  Members

Posted 20 February 2013 - 10:25 PM

On your new picture the letter widths are still different from the texture. If you are using point sampling, try switching to linear filtering and you will see it more clearly that the texture is blurred. Disable blending or add character boxes to your texture in different colors, so you can see each quad matches the corresponding quad in the texture pixel by pixel.

### #14GuardianX  Members

Posted 21 February 2013 - 06:59 AM

Thank you for response, guys.

For your uv's, can you try x / (width-1), (x+w)/(width-1), y / (height-1), (y+h)/(height-1)?

If you're using endpixel, try endpixel-1 / (with-1)

?

and try with with no filtering in the sampler too.

*edit, erm, the other types of filtering i mean.

Well yes, that's what I have done in my font description creator tool. Now, the start texture coordinate is calculated as startPixel/(width-1) and end texture coordinate as endPixel/(width-1). The height is the same for all font letters, since they are placed in single line inside texture. Tried other types of filtering too, but unfortunately with no results.

I know you are trying to do this as a learning exercise, but have you tried just using the PNG version of the texture instead of the DDS?  It would be worth a shot to see if you can get rid of the compression artifacts as a possible source of error.

If you want to see another reference, MJP added his text renderer to Hieroglyph 3.  Take a look in the SpriteRendererDX11 class, and you will see how he is using GDI to build the glyph texture.  I recall having issues if the source texture was not anti-aliased, and if the origin texture size is slightly off from the end size in the render target.

Unfortunately, I'm not familiar with texture loading from file types other than DDS yet. I use Microsoft DDS loader from their tutorials, since I'm writing code using Windows 8 SDK, where lots of D3DX loading functions have been cut off. However, I created a single plane with the size of DDS texture, covering it with that texture, and here is the result:

Upper text is generated by number of planes and fractional texture coordinates. The text in the center of the image is a solid rectangle with single font texture over it. As you can see, latter is displayed fine, so I assume there is no distortion, caused by texture convertion mechanism.

Concerning GDI. Thank you for pointing that out for me, but I hope to use the same text class I'm creating right now in 3D world as well. As far as I understand, GDI is used for 2D text rendering on the window surface (standard Win32 graphics API). The code of Hieroglyph 3 is extremely well written, but it's a little overwhelming project for me as beginner =) That's why I'm trying to create very simple font rendering engine the same way as described in Rastertek tutorial.

On your new picture the letter widths are still different from the texture. If you are using point sampling, try switching to linear filtering and you will see it more clearly that the texture is blurred. Disable blending or add character boxes to your texture in different colors, so you can see each quad matches the corresponding quad in the texture pixel by pixel.

I'm using linear filtering, tho I played with other filters and ever tried to disable Z-buffer, but those actions provided no result. Here is comparison with and without alpha, to emphasize pixel occupation by letter-planes. Pay no attention to spaces between letters, because they are auto-generated and do not belong to either letter geometry:

If that helps, my font texture is 1900x18 pixels:

Not sure why, but it seems that forum engine compressed it, so it's just an example.

And generated coordinates are the following (the line consists of letter, width-in-pixels, height-in-pixels, start texture U coordinate, end texture U coordinate):

: 3 18 0.003159558 0.004212744
, 3 18 0.01421801 0.0152712
. 3 18 0.02632965 0.02738283
! 3 18 0.03791469 0.03896788
@ 7 18 0.04844655 0.05160611
# 8 18 0.059505 0.06319115
~ 8 18 0.07109005 0.07477619
% 7 18 0.08320168 0.08636124
$7 18 0.09478673 0.09794629 ( 3 18 0.1079516 0.1090047 ) 3 18 0.1184834 0.1195366 - 8 18 0.1290153 0.1327014 + 9 18 0.1406003 0.1448131 = 9 18 0.1521854 0.1563981 / 7 18 0.1637704 0.16693 * 7 18 0.175882 0.1790416 ? 7 18 0.1874671 0.1906267 < 9 18 0.1985255 0.2027383 > 9 18 0.2101106 0.2143233 \ 7 18 0.2216956 0.2248552 A 11 18 0.2327541 0.23802 B 8 18 0.2448657 0.2485519 C 9 18 0.2564508 0.2606635 D 9 18 0.2680358 0.2722486 E 8 18 0.2796209 0.283307 F 8 18 0.2912059 0.294892 G 9 18 0.3027909 0.3070037 H 9 18 0.314376 0.3185887 I 7 18 0.3264876 0.3296472 J 9 18 0.3375461 0.3417588 K 9 18 0.3491311 0.3533439 L 9 18 0.3607162 0.3649289 M 11 18 0.3717746 0.3770405 N 9 18 0.3838862 0.388099 O 9 18 0.3954713 0.399684 P 8 18 0.4075829 0.4112691 Q 9 18 0.4186414 0.4228541 R 9 18 0.4302264 0.4344392 S 7 18 0.4423381 0.4454976 T 9 18 0.4533965 0.4576093 U 9 18 0.4649816 0.4691943 V 10 18 0.47604 0.4807793 W 11 18 0.4876251 0.492891 X 10 18 0.4992101 0.5039495 Y 9 18 0.5113217 0.5155345 Z 7 18 0.5234334 0.526593 a 8 18 0.5350184 0.5387046 b 9 18 0.5460769 0.5502896 c 8 18 0.557662 0.5613481 d 9 18 0.5692469 0.5734597 e 8 18 0.580832 0.5845182 f 8 18 0.5929437 0.5966298 g 8 18 0.6040021 0.6076882 h 9 18 0.6155872 0.6197999 i 7 18 0.6276988 0.6308584 j 5 18 0.6392838 0.6413902 k 8 18 0.6508689 0.654555 l 7 18 0.6624539 0.6656135 m 11 18 0.6729858 0.6782517 n 9 18 0.6850974 0.6893101 o 8 18 0.6966825 0.7003686 p 9 18 0.7082675 0.7124802 q 9 18 0.7198526 0.7240653 r 8 18 0.7319642 0.7356504 s 7 18 0.7435492 0.7467088 t 8 18 0.7546077 0.7582939 u 9 18 0.7661927 0.7704055 v 10 18 0.7772512 0.7819905 w 11 18 0.7888362 0.7941021 x 9 18 0.8009478 0.8051606 y 11 18 0.8120063 0.8172722 z 7 18 0.8246446 0.8278041 0 7 18 0.8362296 0.8393891 1 7 18 0.8478146 0.8509742 2 8 18 0.8588731 0.8625593 3 7 18 0.8709847 0.8741443 4 7 18 0.8825698 0.8857293 5 7 18 0.8941548 0.8973144 6 8 18 0.9057398 0.909426 7 7 18 0.9173249 0.9204845 8 7 18 0.92891 0.9320695 9 7 18 0.940495 0.9436545  I think it can be caused by floating point unpresice issues, but I'm not sure how to prove that and how to fix that, if it is the case. For example, consider letter Q (width 9 pixels) will have 0.4186414x1899=795.04320186 start pixel and 0.4228541x1899=802.9999359 end pixel, when DX tries to get texel for concrete pixel. I don't multiply anything in my application, just wondering if DX could interpolate pixels wrong. Tho, there is the same issue with texture coordinates in Rastertek's tutorial, but result text looks just fine in it. Edited by GuardianX, 21 February 2013 - 07:08 AM. ### #15Erik Rufelt Members Posted 21 February 2013 - 07:33 AM The problem is either the texture coordinates or the vertex coordinates for your quads. Are you sure you are using only integer coordinates? If your quad vertices are like 10.1 instead of 10.0 this could happen. If your texture-coordinates are on exact pixel boundaries in the texture then you need to use vertex coordinates without fractional parts too. Also, you should not use 1899, but 1900. Coordinate 1.0 would otherwise be on the left side of the last pixel, where it should be on the right side. Floating point is not an issue, it is precise enough for this case. So if Q starts at 177, 0 in the texture and is 9 pixels wide and 18 pixels high, use coords (177.0/1900.0, 0.0, (177.0+9.0)/1900.0, 1.0). Use vertex-coordinates (x, y, (x + 9.0), (y + 18.0)) to draw it on the screen, where x and y is floor(...) to make sure they are integers. If you later scale your text it's possible you want to include a half pixel border for linear filtering, and as such create texture coordinates at 10.5 / 1900 instead of 10.0 / 1900, at which point you also need to do that for vertex-coords on the screen. Start with integer coords. Edited by Erik Rufelt, 21 February 2013 - 07:33 AM. ### #16GuardianX Members Posted 21 February 2013 - 09:47 AM The problem is either the texture coordinates or the vertex coordinates for your quads. Are you sure you are using only integer coordinates? If your quad vertices are like 10.1 instead of 10.0 this could happen. If your texture-coordinates are on exact pixel boundaries in the texture then you need to use vertex coordinates without fractional parts too. Also, you should not use 1899, but 1900. Coordinate 1.0 would otherwise be on the left side of the last pixel, where it should be on the right side. Floating point is not an issue, it is precise enough for this case. So if Q starts at 177, 0 in the texture and is 9 pixels wide and 18 pixels high, use coords (177.0/1900.0, 0.0, (177.0+9.0)/1900.0, 1.0). Use vertex-coordinates (x, y, (x + 9.0), (y + 18.0)) to draw it on the screen, where x and y is floor(...) to make sure they are integers. If you later scale your text it's possible you want to include a half pixel border for linear filtering, and as such create texture coordinates at 10.5 / 1900 instead of 10.0 / 1900, at which point you also need to do that for vertex-coords on the screen. Start with integer coords. Thanks for response. Coordinates of my quads are float values, but they don't have any fractional parts, I just checked that. For example, when I create a sentence, containing only Q letter, the quad, which I get is: Coordinate 0: 0 -18 0 Texture: 0.418641 1 // bottom-left Coordinate 1: 9 -18 0 Texture: 0.422854 1 // bottom-right Coordinate 2: 0 -0 0 Texture: 0.418641 0 // top-left Coordinate 3: 9 -0 0 Texture: 0.422854 0 // top-right  As you can see for yourself from my previos post, they are accurately formed out of font description file. Those coordinates are then modified in vertex shader by world matrix, which just offsets them to appropriate x,y coordinate system where 0,0 lies on top left of the screen. Without multiplication by world matrix, the quad will be displayed nearly at the center of the screen, but letter will look the same as with world transformation anyway, so this transformation have no impact on letter's bad appearance. Also, doesnt last column of pixels will have an index 1899, if the first column has 0? In that case the last column of pixels will have 1899/1900 texture U coordinate. Shouldn't it be equal to 1? ### #17rukiruki Members Posted 21 February 2013 - 12:13 PM Can you post the formula you're using to calculate UV? For example, consider letter Q (width 9 pixels) will have 0.4186414x1899=795.04320186 start pixel and 0.4228541x1899=802.9999359 end pixel, when DX tries to get texel for concrete pixel. 803 - 795 is not 9 pixels wide Here's mine i use to achieve pixel perfect precision float cRenderBuffer::convertUVDX( int pixelValIn ) { // Return return (float)( pixelValIn ) / (float)( currentTexture->baseDimension - 1 ); }  so 795 should equate to 0.4186413902053712 and 804 should equate to 0.4233807266982622 What you posted seems to be placing a 8 pixel wide uv onto a 9 pixel wide quad, unless I misread! ### #18GuardianX Members Posted 21 February 2013 - 01:03 PM Can you post the formula you're using to calculate UV? For example, consider letter Q (width 9 pixels) will have 0.4186414x1899=795.04320186 start pixel and 0.4228541x1899=802.9999359 end pixel, when DX tries to get texel for concrete pixel. 803 - 795 is not 9 pixels wide Here's mine i use to achieve pixel perfect precision float cRenderBuffer::convertUVDX( int pixelValIn ) { // Return return (float)( pixelValIn ) / (float)( currentTexture->baseDimension - 1 ); }  so 795 should equate to 0.4186413902053712 and 804 should equate to 0.4233807266982622 What you posted seems to be placing a 8 pixel wide uv onto a 9 pixel wide quad, unless I misread! Well, 795 is the start pixel position and 803 is the end pixel horizontal position of Q symbol. That means both should be included when calculating symbol's width. Hence result width is 803 - 795 + 1 = 9. My old algorythm was the same as yours. Anyway, it looks like I have fixed an issue now. I imagined texture as the grid of texels, where each pixel resides between grid-forming lines, and not on them, that's why it cannot have pixelPos/width-1 texture coordinate, since pixelPos itself is 1.0/width-1 wide! It means that to obtain texture coordinate (nearest grid-forming line), I have to decrease symbol's start pixel horizontal position by 0.5 and increase symbol's last pixel horizontal position by 0.5. Here is algorythm I use to analyse PNG font texture written in C#: Bitmap data = new Bitmap(filename); int width = data.Width; int height = data.Height; int letter_start = -1; int letter_end = -1; int current_letter = 0; for (int i = 0; i < width; i++) { bool is_empty_column = true; for (int j = 0; j < height; j++) { if (data.GetPixel(i, j).A != 0) { is_empty_column = false; if (letter_start == -1) { letter_start = i; } } } if (is_empty_column == true) { if (letter_start != -1) { letter_end = i - 1; mapped_alphabet[alphabet[current_letter]] = new LetterInfo(letter_start, letter_end, letter_end - letter_start + 1, height, ((float)letter_start - 0.5f)/((float)width-1.0f), ((float)letter_end + 0.5f)/((float)width-1.0f)); letter_start = -1; current_letter += 1; } } } where alphabet = ":,.!@#~%$()-+=/*?<>\\ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

And the result is:

There are rare occasions of half-transparent symbols, such as 9, but everything else looks good.

Thanks to everyone who had found the time to help! =)

Edited by GuardianX, 21 February 2013 - 01:11 PM.

### #19rukiruki  Members

Posted 21 February 2013 - 01:13 PM

I'm glad you got it working!

I'm confused as to why you're using  "letter_end - letter_start + 1" and "803 - 795 + 1 = 9", the +1 seems to be wrong to me.

If start pixel is 795 and width is 9, you should be passing 795 and 795 + 9 (which is 804) into the UV equation.

u1 = 795 / 1899

u2 = 804 / 1899

And hopefully you then dont have to bother with the 0.5 texel offsets, and it should be pixel perfect

But your way may be fine anyway, it's just the way I've gotten used to. Good luck

### #20GuardianX  Members

Posted 21 February 2013 - 01:45 PM

Wow, I accidentaly found a perfect article, describing the process I tried to explain in my previous post

Hope it will help someone who stuck at this problem just like me.

It describes how you must subtract 0.5 to get corresponding pixel and texel match each other.

I'm glad you got it working!

I'm confused as to why you're using  "letter_end - letter_start + 1" and "803 - 795 + 1 = 9", the +1 seems to be wrong to me.

If start pixel is 795 and width is 9, you should be passing 795 and 795 + 9 (which is 804) into the UV equation.

u1 = 795 / 1899

u2 = 804 / 1899

And hopefully you then dont have to bother with the 0.5 texel offsets, and it should be pixel perfect

But your way may be fine anyway, it's just the way I've gotten used to. Good luck

Take a look at this:

It illustrates my approach more closely.

Thank you for advice, regardless! =)

Edited by GuardianX, 21 February 2013 - 01:46 PM.

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