nanoDLP

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

4K Screen Support - Helps Needed

As you probably know, TI have been introduced 4K DLP chips and couple of brands will release 4K projectors very soon. They probably costs around $4000~$5000 at first.
Anyways I think it will be good idea to be prepared for 4K resolution.

I do not have access to any display with 4K resolution, will appreciate if somebody could test theories below to see if we need improvement on any part of nanodlp.

• RPi already supports 4K.

• Our image display module needs testing. I do not expect any issue except GPU memory allocation (require tweaking config.txt). Also it will increase delay for image display linearly

• nanoDLP already could do slicing and conversation to 4K, I expect drawing speed have linear increase 4 times. I think we are around 200ms per frame for drawing which will be 800ms for 4K. But still needs testing.

• Our memory usage for drawing is low so I do not expect any problem this regard.

• Calibration images needs total rewrite, they should dynamically generated for the target resolution.

adam

Member

Registered: 2016-02-18

Posts: 100

Re: 4K Screen Support - Helps Needed

does drawing speed have any negative impact on the print? The thing that always worries me since Creation Workshop is irregularities in exposure times. As i have times around 950ms for 50micron layers, having a variance of 100-200ms would significantly show in prints, especially for tall, vertical walls.
With CW i measured variance of up to 500ms, which was not acceptable. I have no issues whatsoever with NanoDLP so far.

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: 4K Screen Support - Helps Needed

I totally agree with you, it is getting very important with ever improving resins` cure times.
It is pretty interesting topic. Actually we have pretty good control of everything going on to display an image so we can do lots of improvements.

1. Start measure time
2. Decode Image to the memory
3. Send memory pointer to GPU firmware
4. Firmware copy memory to GPU memory
5. Refresh display
6. Wait until cure time reach target and kill the layer

We have two kind of delays, one is OS level, another one is hardware level.
Currently our time variety is probably around 20ms or less which is on OS level. And total delay is around 40ms(Hardware + OS level).
I think with 4K our delay will increase to 80~100ms(hardware) and 60ms or less for OS level, 140~160ms in total.

For the hardware delays we do not have much of variety, if we could measure it we can add it to the cure time (step 4 and 5).
For the OS level delays majority of delay is belong to step 2. Which is there because it was not significant enough. But it is possible to move it outside of our current loop.
It probably could decrease our delay to ~100ms for 4K.

1. Start measure time
2. Send memory pointer to GPU firmware
3. Firmware copy memory to GPU memory
4. Refresh display
5. Wait until cure time reach target and kill the layer

Another thing which we could do is to cache couple of layers in GPU memory and just switch. I am not sure how much it could decrease 4K delay but my guess is our total delay will be ~70ms.
Good part is that most of that will be static delay which would not cause cure irregularity and make it possible to call image before-head so we could decrease the delay to couple of ms in total and offset static delay.

1. Start measure time
2. Switch layer
3. Wait until cure time reach target and kill the layer

adam

Member

Registered: 2016-02-18

Posts: 100

Re: 4K Screen Support - Helps Needed

I agree, static delay is not much to worry about. Thanks for the extensive explanation

bzb

Member

Registered: 2016-09-08

Posts: 5

Re: 4K Screen Support - Helps Needed

Hello,

I'm about to begin constructing a 4K SLA/LCD printer using nanoDLP but I'm still doing my initial research. Can you please tell me if 4K support is included in latest version of nanoDLP.

Apologies in advance if this topic is closed or I've missed something.

Last edited by bzb (2016-09-08 08:32:24)

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: 4K Screen Support - Helps Needed

nanodlp could support any resolution. There are some limitation on rpi's gpu spec. 4K is support is reported on rpi forum.

bzb

Member

Registered: 2016-09-08

Posts: 5

Re: 4K Screen Support - Helps Needed

Thank you.

bzb

Member

Registered: 2016-09-08

Posts: 5

Re: 4K Screen Support - Helps Needed

Hi again,

I have put together a working system with RPi 3B with 4K monitor @ 24-28Hz and I can test optimizations and/or issues related to removing exposure irregularities in 4K support.

So far I have the beta version installed (for the better slicer) and have successfully displayed the dynamic calibration images in true 4K over hdmi.

However when I start to print nothing is shown on the monitor. Am I missing something? Maybe incorrect nanoDLP configuration on my part?

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: 4K Screen Support - Helps Needed

Maybe you have chosen black color as layer color in profile settings.

bzb

Member

Registered: 2016-09-08

Posts: 5

Re: 4K Screen Support - Helps Needed

Shahin, sorry for the slow answer. Seems like that was the case - I'm doing dry runs on the 4K LCD without issues. Many thanks for pointing out the layer color.

I have another question - I was able to do the dry-runs with the beta version and minimal exposition (3sec) without any noticeable slowdown in 4K (if we ignore slicer slowdown). Does this mean that the above-mentioned optimizations regarding exposure irregularities (i.e. caching layers, etc) have already been implemented in the beta version? If they are not yet implemented, I must say that I'm very impressed with beta performance in 4K.

Last edited by bzb (2016-11-07 09:48:16)

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: 4K Screen Support - Helps Needed

No, nothing implemented for 4K yet. Good to know It does not need any change at-least until 8K

Slicer needs faster memory and cpu hopefully we get RPi 4 soon.

Could you record high frame video and measure real display time compare to the specified cure time?

bzb

Member

Registered: 2016-09-08

Posts: 5

Re: 4K Screen Support - Helps Needed

Sure. It will take some time, however, since I'm doing this in my spare time. Do you need the video itself or just the comparison?

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: 4K Screen Support - Helps Needed

Time comparison will be enough, thank you.

colgeocol

Member

Registered: 2016-09-14

Posts: 23

Re: 4K Screen Support - Helps Needed

bzb

I understand you have your 4K printer working.

Would you show your complete config.txt on the forum so I could copy and paste?

MaxJewels

Member

Registered: 2017-08-10

Posts: 88

Re: 4K Screen Support - Helps Needed

Hi again,

I have put together a working system with RPi 3B with 4K monitor @ 24-28Hz and I can test optimizations and/or issues related to removing exposure irregularities in 4K support.

So far I have the beta version installed (for the better slicer) and have successfully displayed the dynamic calibration images in true 4K over hdmi.

However when I start to print nothing is shown on the monitor. Am I missing something? Maybe incorrect nanoDLP configuration on my part?

I am looking for info on changing my 2k in 4k, could you indicate the type of monitor and the controller you are using?

v112112112

Member

Registered: 2018-04-07

Posts: 11

Re: 4K Screen Support - Helps Needed

Yes,

Someone please post working 4k config.txt I have tried both from raspberrypi.org/forums/viewtopic.php?t=79330 but they do not help the image actually fit inside the screen.

v112112112

Member

Registered: 2018-04-07

Posts: 11

Re: 4K Screen Support - Helps Needed

I worked it out myself thx. Last line of the calibration grid is jumpy ie you can see it drawing the line

royaleclash

Member

Registered: 2018-04-30

Posts: 1

Re: 4K Screen Support - Helps Needed

Shahin, I work at Texas Instruments DLP group and think we may be able to assist in terms of maximizing the performance of nanoDLP software with 3D printing engine enabled by DLP technology. If you're interested, could you leave me an email address that i can use to contact? Thank you.