# Other common issues
## 1. Why is the imported HDRI blurry?
High-definition HDRI takes up more resources when previewing, so the HDRI is compressed to 2k by the D5 when previewing to ensure that accurate lighting is provided.
* The image output is based on the actual size of the imported HDRI.
* The HDRI is also compressed to 2K/4K/8K for video.
## 2. Why does it prompt " Failed to load HDRI"?
Custom HDRIs imported into the D5 renderer need to be standard size files.
Common sizes:
1k
2k
4k
8k
1024×512
2048 × 1024
4096 × 2048
8192 × 4096
> 1. Large HDRIs take longer to import and will take longer to render out.
>
> 2. Recommended HDRI download site: [Poly Haven](https://polyhaven.com/hdris)
>
>
## 3. Why are there two angles of shadow in the scene?
In some HDRIs the sun is visible and already produces clear shadows. If **"Sun-Direction-Custom" is ticked**, it is possible to have this "heavy shadow" problem in certain cases, because there is already a sun in the original HDRI.
The following is recommended for adjusting the sky:
1. **Enable Follow HDRI.
**Make the sun's altitude and azimuth auto-follow the sun in the HDRI. Adjust the angle of the sun by rotating the HDRI.
2. **Replace the HDRI with one that does not have the sunlight effect** (i.e. one that is more balanced in brightness). This will not produce more noticeable shadows, and this time use simulated parallel sunlight will allow you to make more controlled shadows.
3. **Use Geo and Sky.
**Geo-Sky has fewer parameters controllable for the sun compared to HDRI, and is based on real geographic information to determine the sun's orientation and light changes.
## 4. How to adjust the Tyndall effect/volume light?
In the second item of the "Environment" panel on the right sidebar, find **"Weather" > select "Fog" > enable the "Volume Light" button**.
* Volume Light: The Tyndall effect is a phenomenon in which light is scattered by particles in the air, allowing pathways of light to be seen.
* Scattering: Controls the scattering distribution of the Volume Light scattering effect. The default value is 0 for a uniformly light fog, adjusting it to 1 will make the fog brighter from the direction of the light source.
::: tip Note
The issue of "preview is normal but output has no Tyndall effect" has been fixed in 2.9 version, please output with 2.9 version.
:::
::: tip Note
If you get ‘stripes of light’ when creating the Tyndall effect/Volume Light, this is a known issue with the current 2.9 version. Please try giving the one-sided wall a certain thickness (or placing a plane outside the wall).
:::
stripes of ligh & placing a plane outside the wall
## 5. How do I achieve the effect of no precipitation but having standing water/snow?
1. **Precipitation:** Turn on precipitation in Environment - Weather, adjust the precipitation strength to 0, and then increase the puddle parameter appropriately.
2. **Decals:** The effect of water on the ground can also be achieved with a custom transparency map.
Adjust the Precipitation strength to 0, and increase the Puddle parameter appropriately
## 6. Why is the custom HDRI/LUT file import not working?
This will occur if the file path of the custom HDRI/LUT file contains special characters.
It is recommended that the HDRI/LUT file be placed under an English path.
## 7. Why do scenes lose HDRI thumbnails?
There are two cases that can occur in the current version:
* Load an old archive and that archive uses the D5 inbuilt HDRI - Pure White;
* Download the HDRI from the D5 Assets Library - HDRI and import its local cache.
## 8. When keyframing the environment (Geo and Sky/HDRI), why does the scene flicker/have white spots?
It's a current KNOWN ISSUE.
It is relatively difficult to downsample in this case (when the scene environment changes), thus white spots/scene flickering may occur during preview or output.
Suggestion: When keyframing the environment in animations, if white spots/flickering occurs, it is recommended to output in two separate times and merge them in the post-production software.
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## 9. Why do scenes created in version 3.0 appear different when opened in previous versions?
When opening files saved in version 3.0 using previous D5 versions, **the manual exposure** and **fog effects** may alter, requiring manual adjustment of the parameters.
