A wearable computing device, comprising: a processing unit; a memory coupled to the processing unit and storing instructions which, when executed by the processing unit, perform acts comprising: acquiring at least one image of an environment where the wearable computing device is located, the at least one image being captured by a camera that operatively communicates with the wearable computing device; generating at least one adjusted image by adjusting pixel values of the at least one image based on a camera parameter used by the camera in capturing the at least one image; determining ambient light information that indicates light intensities in a plurality of directions in the environment, wherein said determining of the ambient light information is based on the at least one adjusted image; and rendering a mixed reality object to a user of the wearable computing device based on the ambient light information, such that the user can see the mixed reality object having an ambient light effect, characterised in that the rendering of the mixed reality object based on the ambient light information comprises: generating an initial light map associated with the mixed reality object based on the ambient light information; down-sampling the initial light map to generate a set of down-sampled light maps having different resolutions; and rendering the mixed reality object based on the set of down-sampled light maps. a processing unit; a memory coupled to the processing unit and storing instructions which, when executed by the processing unit, perform acts comprising: acquiring at least one image of an environment where the wearable computing device is located, the at least one image being captured by a camera that operatively communicates with the wearable computing device; generating at least one adjusted image by adjusting pixel values of the at least one image based on a camera parameter used by the camera in capturing the at least one image; determining ambient light information that indicates light intensities in a plurality of directions in the environment, wherein said determining of the ambient light information is based on the at least one adjusted image; and rendering a mixed reality object to a user of the wearable computing device based on the ambient light information, such that the user can see the mixed reality object having an ambient light effect, acquiring at least one image of an environment where the wearable computing device is located, the at least one image being captured by a camera that operatively communicates with the wearable computing device; generating at least one adjusted image by adjusting pixel values of the at least one image based on a camera parameter used by the camera in capturing the at least one image; determining ambient light information that indicates light intensities in a plurality of directions in the environment, wherein said determining of the ambient light information is based on the at least one adjusted image; and rendering a mixed reality object to a user of the wearable computing device based on the ambient light information, such that the user can see the mixed reality object having an ambient light effect, characterised in that the rendering of the mixed reality object based on the ambient light information comprises: generating an initial light map associated with the mixed reality object based on the ambient light information; down-sampling the initial light map to generate a set of down-sampled light maps having different resolutions; and rendering the mixed reality object based on the set of down-sampled light maps. generating an initial light map associated with the mixed reality object based on the ambient light information; down-sampling the initial light map to generate a set of down-sampled light maps having different resolutions; and rendering the mixed reality object based on the set of down-sampled light maps.